| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
userfaultfd: fix checks for huge PMDs
Patch series "userfaultfd: fix races around pmd_trans_huge() check", v2.
The pmd_trans_huge() code in mfill_atomic() is wrong in three different
ways depending on kernel version:
1. The pmd_trans_huge() check is racy and can lead to a BUG_ON() (if you hit
the right two race windows) - I've tested this in a kernel build with
some extra mdelay() calls. See the commit message for a description
of the race scenario.
On older kernels (before 6.5), I think the same bug can even
theoretically lead to accessing transhuge page contents as a page table
if you hit the right 5 narrow race windows (I haven't tested this case).
2. As pointed out by Qi Zheng, pmd_trans_huge() is not sufficient for
detecting PMDs that don't point to page tables.
On older kernels (before 6.5), you'd just have to win a single fairly
wide race to hit this.
I've tested this on 6.1 stable by racing migration (with a mdelay()
patched into try_to_migrate()) against UFFDIO_ZEROPAGE - on my x86
VM, that causes a kernel oops in ptlock_ptr().
3. On newer kernels (>=6.5), for shmem mappings, khugepaged is allowed
to yank page tables out from under us (though I haven't tested that),
so I think the BUG_ON() checks in mfill_atomic() are just wrong.
I decided to write two separate fixes for these (one fix for bugs 1+2, one
fix for bug 3), so that the first fix can be backported to kernels
affected by bugs 1+2.
This patch (of 2):
This fixes two issues.
I discovered that the following race can occur:
mfill_atomic other thread
============ ============
<zap PMD>
pmdp_get_lockless() [reads none pmd]
<bail if trans_huge>
<if none:>
<pagefault creates transhuge zeropage>
__pte_alloc [no-op]
<zap PMD>
<bail if pmd_trans_huge(*dst_pmd)>
BUG_ON(pmd_none(*dst_pmd))
I have experimentally verified this in a kernel with extra mdelay() calls;
the BUG_ON(pmd_none(*dst_pmd)) triggers.
On kernels newer than commit 0d940a9b270b ("mm/pgtable: allow
pte_offset_map[_lock]() to fail"), this can't lead to anything worse than
a BUG_ON(), since the page table access helpers are actually designed to
deal with page tables concurrently disappearing; but on older kernels
(<=6.4), I think we could probably theoretically race past the two
BUG_ON() checks and end up treating a hugepage as a page table.
The second issue is that, as Qi Zheng pointed out, there are other types
of huge PMDs that pmd_trans_huge() can't catch: devmap PMDs and swap PMDs
(in particular, migration PMDs).
On <=6.4, this is worse than the first issue: If mfill_atomic() runs on a
PMD that contains a migration entry (which just requires winning a single,
fairly wide race), it will pass the PMD to pte_offset_map_lock(), which
assumes that the PMD points to a page table.
Breakage follows: First, the kernel tries to take the PTE lock (which will
crash or maybe worse if there is no "struct page" for the address bits in
the migration entry PMD - I think at least on X86 there usually is no
corresponding "struct page" thanks to the PTE inversion mitigation, amd64
looks different).
If that didn't crash, the kernel would next try to write a PTE into what
it wrongly thinks is a page table.
As part of fixing these issues, get rid of the check for pmd_trans_huge()
before __pte_alloc() - that's redundant, we're going to have to check for
that after the __pte_alloc() anyway.
Backport note: pmdp_get_lockless() is pmd_read_atomic() in older kernels. |
| In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: Validate function returns
[WHAT & HOW]
Function return values must be checked before data can be used
in subsequent functions.
This fixes 4 CHECKED_RETURN issues reported by Coverity. |
| In the Linux kernel, the following vulnerability has been resolved:
ice: protect XDP configuration with a mutex
The main threat to data consistency in ice_xdp() is a possible asynchronous
PF reset. It can be triggered by a user or by TX timeout handler.
XDP setup and PF reset code access the same resources in the following
sections:
* ice_vsi_close() in ice_prepare_for_reset() - already rtnl-locked
* ice_vsi_rebuild() for the PF VSI - not protected
* ice_vsi_open() - already rtnl-locked
With an unfortunate timing, such accesses can result in a crash such as the
one below:
[ +1.999878] ice 0000:b1:00.0: Registered XDP mem model MEM_TYPE_XSK_BUFF_POOL on Rx ring 14
[ +2.002992] ice 0000:b1:00.0: Registered XDP mem model MEM_TYPE_XSK_BUFF_POOL on Rx ring 18
[Mar15 18:17] ice 0000:b1:00.0 ens801f0np0: NETDEV WATCHDOG: CPU: 38: transmit queue 14 timed out 80692736 ms
[ +0.000093] ice 0000:b1:00.0 ens801f0np0: tx_timeout: VSI_num: 6, Q 14, NTC: 0x0, HW_HEAD: 0x0, NTU: 0x0, INT: 0x4000001
[ +0.000012] ice 0000:b1:00.0 ens801f0np0: tx_timeout recovery level 1, txqueue 14
[ +0.394718] ice 0000:b1:00.0: PTP reset successful
[ +0.006184] BUG: kernel NULL pointer dereference, address: 0000000000000098
[ +0.000045] #PF: supervisor read access in kernel mode
[ +0.000023] #PF: error_code(0x0000) - not-present page
[ +0.000023] PGD 0 P4D 0
[ +0.000018] Oops: 0000 [#1] PREEMPT SMP NOPTI
[ +0.000023] CPU: 38 PID: 7540 Comm: kworker/38:1 Not tainted 6.8.0-rc7 #1
[ +0.000031] Hardware name: Intel Corporation S2600WFT/S2600WFT, BIOS SE5C620.86B.02.01.0014.082620210524 08/26/2021
[ +0.000036] Workqueue: ice ice_service_task [ice]
[ +0.000183] RIP: 0010:ice_clean_tx_ring+0xa/0xd0 [ice]
[...]
[ +0.000013] Call Trace:
[ +0.000016] <TASK>
[ +0.000014] ? __die+0x1f/0x70
[ +0.000029] ? page_fault_oops+0x171/0x4f0
[ +0.000029] ? schedule+0x3b/0xd0
[ +0.000027] ? exc_page_fault+0x7b/0x180
[ +0.000022] ? asm_exc_page_fault+0x22/0x30
[ +0.000031] ? ice_clean_tx_ring+0xa/0xd0 [ice]
[ +0.000194] ice_free_tx_ring+0xe/0x60 [ice]
[ +0.000186] ice_destroy_xdp_rings+0x157/0x310 [ice]
[ +0.000151] ice_vsi_decfg+0x53/0xe0 [ice]
[ +0.000180] ice_vsi_rebuild+0x239/0x540 [ice]
[ +0.000186] ice_vsi_rebuild_by_type+0x76/0x180 [ice]
[ +0.000145] ice_rebuild+0x18c/0x840 [ice]
[ +0.000145] ? delay_tsc+0x4a/0xc0
[ +0.000022] ? delay_tsc+0x92/0xc0
[ +0.000020] ice_do_reset+0x140/0x180 [ice]
[ +0.000886] ice_service_task+0x404/0x1030 [ice]
[ +0.000824] process_one_work+0x171/0x340
[ +0.000685] worker_thread+0x277/0x3a0
[ +0.000675] ? preempt_count_add+0x6a/0xa0
[ +0.000677] ? _raw_spin_lock_irqsave+0x23/0x50
[ +0.000679] ? __pfx_worker_thread+0x10/0x10
[ +0.000653] kthread+0xf0/0x120
[ +0.000635] ? __pfx_kthread+0x10/0x10
[ +0.000616] ret_from_fork+0x2d/0x50
[ +0.000612] ? __pfx_kthread+0x10/0x10
[ +0.000604] ret_from_fork_asm+0x1b/0x30
[ +0.000604] </TASK>
The previous way of handling this through returning -EBUSY is not viable,
particularly when destroying AF_XDP socket, because the kernel proceeds
with removal anyway.
There is plenty of code between those calls and there is no need to create
a large critical section that covers all of them, same as there is no need
to protect ice_vsi_rebuild() with rtnl_lock().
Add xdp_state_lock mutex to protect ice_vsi_rebuild() and ice_xdp().
Leaving unprotected sections in between would result in two states that
have to be considered:
1. when the VSI is closed, but not yet rebuild
2. when VSI is already rebuild, but not yet open
The latter case is actually already handled through !netif_running() case,
we just need to adjust flag checking a little. The former one is not as
trivial, because between ice_vsi_close() and ice_vsi_rebuild(), a lot of
hardware interaction happens, this can make adding/deleting rings exit
with an error. Luckily, VSI rebuild is pending and can apply new
configuration for us in a managed fashion.
Therefore, add an additional VSI state flag ICE_VSI_REBUILD_PENDING to
indicate that ice_x
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: Ensure array index tg_inst won't be -1
[WHY & HOW]
tg_inst will be a negative if timing_generator_count equals 0, which
should be checked before used.
This fixes 2 OVERRUN issues reported by Coverity. |
| In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: Check index for aux_rd_interval before using
aux_rd_interval has size of 7 and should be checked.
This fixes 3 OVERRUN and 1 INTEGER_OVERFLOW issues reported by Coverity. |
| In the Linux kernel, the following vulnerability has been resolved:
pktgen: use cpus_read_lock() in pg_net_init()
I have seen the WARN_ON(smp_processor_id() != cpu) firing
in pktgen_thread_worker() during tests.
We must use cpus_read_lock()/cpus_read_unlock()
around the for_each_online_cpu(cpu) loop.
While we are at it use WARN_ON_ONCE() to avoid a possible syslog flood. |
| In the Linux kernel, the following vulnerability has been resolved:
btrfs: do not BUG_ON() when freeing tree block after error
When freeing a tree block, at btrfs_free_tree_block(), if we fail to
create a delayed reference we don't deal with the error and just do a
BUG_ON(). The error most likely to happen is -ENOMEM, and we have a
comment mentioning that only -ENOMEM can happen, but that is not true,
because in case qgroups are enabled any error returned from
btrfs_qgroup_trace_extent_post() (can be -EUCLEAN or anything returned
from btrfs_search_slot() for example) can be propagated back to
btrfs_free_tree_block().
So stop doing a BUG_ON() and return the error to the callers and make
them abort the transaction to prevent leaking space. Syzbot was
triggering this, likely due to memory allocation failure injection. |
| In the Linux kernel, the following vulnerability has been resolved:
serial: sc16is7xx: fix TX fifo corruption
Sometimes, when a packet is received on channel A at almost the same time
as a packet is about to be transmitted on channel B, we observe with a
logic analyzer that the received packet on channel A is transmitted on
channel B. In other words, the Tx buffer data on channel B is corrupted
with data from channel A.
The problem appeared since commit 4409df5866b7 ("serial: sc16is7xx: change
EFR lock to operate on each channels"), which changed the EFR locking to
operate on each channel instead of chip-wise.
This commit has introduced a regression, because the EFR lock is used not
only to protect the EFR registers access, but also, in a very obscure and
undocumented way, to protect access to the data buffer, which is shared by
the Tx and Rx handlers, but also by each channel of the IC.
Fix this regression first by switching to kfifo_out_linear_ptr() in
sc16is7xx_handle_tx() to eliminate the need for a shared Rx/Tx buffer.
Secondly, replace the chip-wise Rx buffer with a separate Rx buffer for
each channel. |
| In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix to do sanity check on F2FS_INLINE_DATA flag in inode during GC
syzbot reports a f2fs bug as below:
------------[ cut here ]------------
kernel BUG at fs/f2fs/inline.c:258!
CPU: 1 PID: 34 Comm: kworker/u8:2 Not tainted 6.9.0-rc6-syzkaller-00012-g9e4bc4bcae01 #0
RIP: 0010:f2fs_write_inline_data+0x781/0x790 fs/f2fs/inline.c:258
Call Trace:
f2fs_write_single_data_page+0xb65/0x1d60 fs/f2fs/data.c:2834
f2fs_write_cache_pages fs/f2fs/data.c:3133 [inline]
__f2fs_write_data_pages fs/f2fs/data.c:3288 [inline]
f2fs_write_data_pages+0x1efe/0x3a90 fs/f2fs/data.c:3315
do_writepages+0x35b/0x870 mm/page-writeback.c:2612
__writeback_single_inode+0x165/0x10b0 fs/fs-writeback.c:1650
writeback_sb_inodes+0x905/0x1260 fs/fs-writeback.c:1941
wb_writeback+0x457/0xce0 fs/fs-writeback.c:2117
wb_do_writeback fs/fs-writeback.c:2264 [inline]
wb_workfn+0x410/0x1090 fs/fs-writeback.c:2304
process_one_work kernel/workqueue.c:3254 [inline]
process_scheduled_works+0xa12/0x17c0 kernel/workqueue.c:3335
worker_thread+0x86d/0xd70 kernel/workqueue.c:3416
kthread+0x2f2/0x390 kernel/kthread.c:388
ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
The root cause is: inline_data inode can be fuzzed, so that there may
be valid blkaddr in its direct node, once f2fs triggers background GC
to migrate the block, it will hit f2fs_bug_on() during dirty page
writeback.
Let's add sanity check on F2FS_INLINE_DATA flag in inode during GC,
so that, it can forbid migrating inline_data inode's data block for
fixing. |
| In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix to cover read extent cache access with lock
syzbot reports a f2fs bug as below:
BUG: KASAN: slab-use-after-free in sanity_check_extent_cache+0x370/0x410 fs/f2fs/extent_cache.c:46
Read of size 4 at addr ffff8880739ab220 by task syz-executor200/5097
CPU: 0 PID: 5097 Comm: syz-executor200 Not tainted 6.9.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x169/0x550 mm/kasan/report.c:488
kasan_report+0x143/0x180 mm/kasan/report.c:601
sanity_check_extent_cache+0x370/0x410 fs/f2fs/extent_cache.c:46
do_read_inode fs/f2fs/inode.c:509 [inline]
f2fs_iget+0x33e1/0x46e0 fs/f2fs/inode.c:560
f2fs_nfs_get_inode+0x74/0x100 fs/f2fs/super.c:3237
generic_fh_to_dentry+0x9f/0xf0 fs/libfs.c:1413
exportfs_decode_fh_raw+0x152/0x5f0 fs/exportfs/expfs.c:444
exportfs_decode_fh+0x3c/0x80 fs/exportfs/expfs.c:584
do_handle_to_path fs/fhandle.c:155 [inline]
handle_to_path fs/fhandle.c:210 [inline]
do_handle_open+0x495/0x650 fs/fhandle.c:226
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
We missed to cover sanity_check_extent_cache() w/ extent cache lock,
so, below race case may happen, result in use after free issue.
- f2fs_iget
- do_read_inode
- f2fs_init_read_extent_tree
: add largest extent entry in to cache
- shrink
- f2fs_shrink_read_extent_tree
- __shrink_extent_tree
- __detach_extent_node
: drop largest extent entry
- sanity_check_extent_cache
: access et->largest w/o lock
let's refactor sanity_check_extent_cache() to avoid extent cache access
and call it before f2fs_init_read_extent_tree() to fix this issue. |
| In the Linux kernel, the following vulnerability has been resolved:
nvme: apple: fix device reference counting
Drivers must call nvme_uninit_ctrl after a successful nvme_init_ctrl.
Split the allocation side out to make the error handling boundary easier
to navigate. The apple driver had been doing this wrong, leaking the
controller device memory on a tagset failure. |
| In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: Fix null pointer deref in dcn20_resource.c
Fixes a hang thats triggered when MPV is run on a DCN401 dGPU:
mpv --hwdec=vaapi --vo=gpu --hwdec-codecs=all
and then enabling fullscreen playback (double click on the video)
The following calltrace will be seen:
[ 181.843989] BUG: kernel NULL pointer dereference, address: 0000000000000000
[ 181.843997] #PF: supervisor instruction fetch in kernel mode
[ 181.844003] #PF: error_code(0x0010) - not-present page
[ 181.844009] PGD 0 P4D 0
[ 181.844020] Oops: 0010 [#1] PREEMPT SMP NOPTI
[ 181.844028] CPU: 6 PID: 1892 Comm: gnome-shell Tainted: G W OE 6.5.0-41-generic #41~22.04.2-Ubuntu
[ 181.844038] Hardware name: System manufacturer System Product Name/CROSSHAIR VI HERO, BIOS 6302 10/23/2018
[ 181.844044] RIP: 0010:0x0
[ 181.844079] Code: Unable to access opcode bytes at 0xffffffffffffffd6.
[ 181.844084] RSP: 0018:ffffb593c2b8f7b0 EFLAGS: 00010246
[ 181.844093] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000004
[ 181.844099] RDX: ffffb593c2b8f804 RSI: ffffb593c2b8f7e0 RDI: ffff9e3c8e758400
[ 181.844105] RBP: ffffb593c2b8f7b8 R08: ffffb593c2b8f9c8 R09: ffffb593c2b8f96c
[ 181.844110] R10: 0000000000000000 R11: 0000000000000000 R12: ffffb593c2b8f9c8
[ 181.844115] R13: 0000000000000001 R14: ffff9e3c88000000 R15: 0000000000000005
[ 181.844121] FS: 00007c6e323bb5c0(0000) GS:ffff9e3f85f80000(0000) knlGS:0000000000000000
[ 181.844128] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 181.844134] CR2: ffffffffffffffd6 CR3: 0000000140fbe000 CR4: 00000000003506e0
[ 181.844141] Call Trace:
[ 181.844146] <TASK>
[ 181.844153] ? show_regs+0x6d/0x80
[ 181.844167] ? __die+0x24/0x80
[ 181.844179] ? page_fault_oops+0x99/0x1b0
[ 181.844192] ? do_user_addr_fault+0x31d/0x6b0
[ 181.844204] ? exc_page_fault+0x83/0x1b0
[ 181.844216] ? asm_exc_page_fault+0x27/0x30
[ 181.844237] dcn20_get_dcc_compression_cap+0x23/0x30 [amdgpu]
[ 181.845115] amdgpu_dm_plane_validate_dcc.constprop.0+0xe5/0x180 [amdgpu]
[ 181.845985] amdgpu_dm_plane_fill_plane_buffer_attributes+0x300/0x580 [amdgpu]
[ 181.846848] fill_dc_plane_info_and_addr+0x258/0x350 [amdgpu]
[ 181.847734] fill_dc_plane_attributes+0x162/0x350 [amdgpu]
[ 181.848748] dm_update_plane_state.constprop.0+0x4e3/0x6b0 [amdgpu]
[ 181.849791] ? dm_update_plane_state.constprop.0+0x4e3/0x6b0 [amdgpu]
[ 181.850840] amdgpu_dm_atomic_check+0xdfe/0x1760 [amdgpu] |
| In the Linux kernel, the following vulnerability has been resolved:
RDMA/hns: Fix soft lockup under heavy CEQE load
CEQEs are handled in interrupt handler currently. This may cause the
CPU core staying in interrupt context too long and lead to soft lockup
under heavy load.
Handle CEQEs in BH workqueue and set an upper limit for the number of
CEQE handled by a single call of work handler. |
| In the Linux kernel, the following vulnerability has been resolved:
soc: qcom: icc-bwmon: Fix refcount imbalance seen during bwmon_remove
The following warning is seen during bwmon_remove due to refcount
imbalance, fix this by releasing the OPPs after use.
Logs:
WARNING: at drivers/opp/core.c:1640 _opp_table_kref_release+0x150/0x158
Hardware name: Qualcomm Technologies, Inc. X1E80100 CRD (DT)
...
Call trace:
_opp_table_kref_release+0x150/0x158
dev_pm_opp_remove_table+0x100/0x1b4
devm_pm_opp_of_table_release+0x10/0x1c
devm_action_release+0x14/0x20
devres_release_all+0xa4/0x104
device_unbind_cleanup+0x18/0x60
device_release_driver_internal+0x1ec/0x228
driver_detach+0x50/0x98
bus_remove_driver+0x6c/0xbc
driver_unregister+0x30/0x60
platform_driver_unregister+0x14/0x20
bwmon_driver_exit+0x18/0x524 [icc_bwmon]
__arm64_sys_delete_module+0x184/0x264
invoke_syscall+0x48/0x118
el0_svc_common.constprop.0+0xc8/0xe8
do_el0_svc+0x20/0x2c
el0_svc+0x34/0xdc
el0t_64_sync_handler+0x13c/0x158
el0t_64_sync+0x190/0x194
--[ end trace 0000000000000000 ]--- |
| In the Linux kernel, the following vulnerability has been resolved:
PCI: endpoint: pci-epf-test: Make use of cached 'epc_features' in pci_epf_test_core_init()
Instead of getting the epc_features from pci_epc_get_features() API, use
the cached pci_epf_test::epc_features value to avoid the NULL check. Since
the NULL check is already performed in pci_epf_test_bind(), having one more
check in pci_epf_test_core_init() is redundant and it is not possible to
hit the NULL pointer dereference.
Also with commit a01e7214bef9 ("PCI: endpoint: Remove "core_init_notifier"
flag"), 'epc_features' got dereferenced without the NULL check, leading to
the following false positive Smatch warning:
drivers/pci/endpoint/functions/pci-epf-test.c:784 pci_epf_test_core_init() error: we previously assumed 'epc_features' could be null (see line 747)
Thus, remove the redundant NULL check and also use the epc_features::
{msix_capable/msi_capable} flags directly to avoid local variables.
[kwilczynski: commit log] |
| In the Linux kernel, the following vulnerability has been resolved:
kvm: s390: Reject memory region operations for ucontrol VMs
This change rejects the KVM_SET_USER_MEMORY_REGION and
KVM_SET_USER_MEMORY_REGION2 ioctls when called on a ucontrol VM.
This is necessary since ucontrol VMs have kvm->arch.gmap set to 0 and
would thus result in a null pointer dereference further in.
Memory management needs to be performed in userspace and using the
ioctls KVM_S390_UCAS_MAP and KVM_S390_UCAS_UNMAP.
Also improve s390 specific documentation for KVM_SET_USER_MEMORY_REGION
and KVM_SET_USER_MEMORY_REGION2.
[frankja@linux.ibm.com: commit message spelling fix, subject prefix fix] |
| In the Linux kernel, the following vulnerability has been resolved:
spi: microchip-core: ensure TX and RX FIFOs are empty at start of a transfer
While transmitting with rx_len == 0, the RX FIFO is not going to be
emptied in the interrupt handler. A subsequent transfer could then
read crap from the previous transfer out of the RX FIFO into the
start RX buffer. The core provides a register that will empty the RX and
TX FIFOs, so do that before each transfer. |
| In the Linux kernel, the following vulnerability has been resolved:
mm/filemap: make MAX_PAGECACHE_ORDER acceptable to xarray
Patch series "mm/filemap: Limit page cache size to that supported by
xarray", v2.
Currently, xarray can't support arbitrary page cache size. More details
can be found from the WARN_ON() statement in xas_split_alloc(). In our
test whose code is attached below, we hit the WARN_ON() on ARM64 system
where the base page size is 64KB and huge page size is 512MB. The issue
was reported long time ago and some discussions on it can be found here
[1].
[1] https://www.spinics.net/lists/linux-xfs/msg75404.html
In order to fix the issue, we need to adjust MAX_PAGECACHE_ORDER to one
supported by xarray and avoid PMD-sized page cache if needed. The code
changes are suggested by David Hildenbrand.
PATCH[1] adjusts MAX_PAGECACHE_ORDER to that supported by xarray
PATCH[2-3] avoids PMD-sized page cache in the synchronous readahead path
PATCH[4] avoids PMD-sized page cache for shmem files if needed
Test program
============
# cat test.c
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/syscall.h>
#include <sys/mman.h>
#define TEST_XFS_FILENAME "/tmp/data"
#define TEST_SHMEM_FILENAME "/dev/shm/data"
#define TEST_MEM_SIZE 0x20000000
int main(int argc, char **argv)
{
const char *filename;
int fd = 0;
void *buf = (void *)-1, *p;
int pgsize = getpagesize();
int ret;
if (pgsize != 0x10000) {
fprintf(stderr, "64KB base page size is required\n");
return -EPERM;
}
system("echo force > /sys/kernel/mm/transparent_hugepage/shmem_enabled");
system("rm -fr /tmp/data");
system("rm -fr /dev/shm/data");
system("echo 1 > /proc/sys/vm/drop_caches");
/* Open xfs or shmem file */
filename = TEST_XFS_FILENAME;
if (argc > 1 && !strcmp(argv[1], "shmem"))
filename = TEST_SHMEM_FILENAME;
fd = open(filename, O_CREAT | O_RDWR | O_TRUNC);
if (fd < 0) {
fprintf(stderr, "Unable to open <%s>\n", filename);
return -EIO;
}
/* Extend file size */
ret = ftruncate(fd, TEST_MEM_SIZE);
if (ret) {
fprintf(stderr, "Error %d to ftruncate()\n", ret);
goto cleanup;
}
/* Create VMA */
buf = mmap(NULL, TEST_MEM_SIZE,
PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (buf == (void *)-1) {
fprintf(stderr, "Unable to mmap <%s>\n", filename);
goto cleanup;
}
fprintf(stdout, "mapped buffer at 0x%p\n", buf);
ret = madvise(buf, TEST_MEM_SIZE, MADV_HUGEPAGE);
if (ret) {
fprintf(stderr, "Unable to madvise(MADV_HUGEPAGE)\n");
goto cleanup;
}
/* Populate VMA */
ret = madvise(buf, TEST_MEM_SIZE, MADV_POPULATE_WRITE);
if (ret) {
fprintf(stderr, "Error %d to madvise(MADV_POPULATE_WRITE)\n", ret);
goto cleanup;
}
/* Punch the file to enforce xarray split */
ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
TEST_MEM_SIZE - pgsize, pgsize);
if (ret)
fprintf(stderr, "Error %d to fallocate()\n", ret);
cleanup:
if (buf != (void *)-1)
munmap(buf, TEST_MEM_SIZE);
if (fd > 0)
close(fd);
return 0;
}
# gcc test.c -o test
# cat /proc/1/smaps | grep KernelPageSize | head -n 1
KernelPageSize: 64 kB
# ./test shmem
:
------------[ cut here ]------------
WARNING: CPU: 17 PID: 5253 at lib/xarray.c:1025 xas_split_alloc+0xf8/0x128
Modules linked in: nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib \
nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct \
nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 \
ip_set nf_tables rfkill nfnetlink vfat fat virtio_balloon \
drm fuse xfs libcrc32c crct10dif_ce ghash_ce sha2_ce sha256_arm64 \
virtio_net sha1_ce net_failover failover virtio_console virtio_blk \
dimlib virtio_mmio
CPU: 17 PID: 5253 Comm: test Kdump: loaded Tainted: G W 6.10.0-rc5-gavin+ #12
Hardware name: QEMU KVM Virtual Machine, BIOS edk2-20240524-1.el9 05/24/2024
pstate: 83400005 (Nzcv daif +PAN -UAO +TC
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
mm/shmem: disable PMD-sized page cache if needed
For shmem files, it's possible that PMD-sized page cache can't be
supported by xarray. For example, 512MB page cache on ARM64 when the base
page size is 64KB can't be supported by xarray. It leads to errors as the
following messages indicate when this sort of xarray entry is split.
WARNING: CPU: 34 PID: 7578 at lib/xarray.c:1025 xas_split_alloc+0xf8/0x128
Modules linked in: binfmt_misc nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 \
nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject \
nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 \
ip_set rfkill nf_tables nfnetlink vfat fat virtio_balloon drm fuse xfs \
libcrc32c crct10dif_ce ghash_ce sha2_ce sha256_arm64 sha1_ce virtio_net \
net_failover virtio_console virtio_blk failover dimlib virtio_mmio
CPU: 34 PID: 7578 Comm: test Kdump: loaded Tainted: G W 6.10.0-rc5-gavin+ #9
Hardware name: QEMU KVM Virtual Machine, BIOS edk2-20240524-1.el9 05/24/2024
pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : xas_split_alloc+0xf8/0x128
lr : split_huge_page_to_list_to_order+0x1c4/0x720
sp : ffff8000882af5f0
x29: ffff8000882af5f0 x28: ffff8000882af650 x27: ffff8000882af768
x26: 0000000000000cc0 x25: 000000000000000d x24: ffff00010625b858
x23: ffff8000882af650 x22: ffffffdfc0900000 x21: 0000000000000000
x20: 0000000000000000 x19: ffffffdfc0900000 x18: 0000000000000000
x17: 0000000000000000 x16: 0000018000000000 x15: 52f8004000000000
x14: 0000e00000000000 x13: 0000000000002000 x12: 0000000000000020
x11: 52f8000000000000 x10: 52f8e1c0ffff6000 x9 : ffffbeb9619a681c
x8 : 0000000000000003 x7 : 0000000000000000 x6 : ffff00010b02ddb0
x5 : ffffbeb96395e378 x4 : 0000000000000000 x3 : 0000000000000cc0
x2 : 000000000000000d x1 : 000000000000000c x0 : 0000000000000000
Call trace:
xas_split_alloc+0xf8/0x128
split_huge_page_to_list_to_order+0x1c4/0x720
truncate_inode_partial_folio+0xdc/0x160
shmem_undo_range+0x2bc/0x6a8
shmem_fallocate+0x134/0x430
vfs_fallocate+0x124/0x2e8
ksys_fallocate+0x4c/0xa0
__arm64_sys_fallocate+0x24/0x38
invoke_syscall.constprop.0+0x7c/0xd8
do_el0_svc+0xb4/0xd0
el0_svc+0x44/0x1d8
el0t_64_sync_handler+0x134/0x150
el0t_64_sync+0x17c/0x180
Fix it by disabling PMD-sized page cache when HPAGE_PMD_ORDER is larger
than MAX_PAGECACHE_ORDER. As Matthew Wilcox pointed, the page cache in a
shmem file isn't represented by a multi-index entry and doesn't have this
limitation when the xarry entry is split until commit 6b24ca4a1a8d ("mm:
Use multi-index entries in the page cache"). |
| In the Linux kernel, the following vulnerability has been resolved:
bpf: Fail bpf_timer_cancel when callback is being cancelled
Given a schedule:
timer1 cb timer2 cb
bpf_timer_cancel(timer2); bpf_timer_cancel(timer1);
Both bpf_timer_cancel calls would wait for the other callback to finish
executing, introducing a lockup.
Add an atomic_t count named 'cancelling' in bpf_hrtimer. This keeps
track of all in-flight cancellation requests for a given BPF timer.
Whenever cancelling a BPF timer, we must check if we have outstanding
cancellation requests, and if so, we must fail the operation with an
error (-EDEADLK) since cancellation is synchronous and waits for the
callback to finish executing. This implies that we can enter a deadlock
situation involving two or more timer callbacks executing in parallel
and attempting to cancel one another.
Note that we avoid incrementing the cancelling counter for the target
timer (the one being cancelled) if bpf_timer_cancel is not invoked from
a callback, to avoid spurious errors. The whole point of detecting
cur->cancelling and returning -EDEADLK is to not enter a busy wait loop
(which may or may not lead to a lockup). This does not apply in case the
caller is in a non-callback context, the other side can continue to
cancel as it sees fit without running into errors.
Background on prior attempts:
Earlier versions of this patch used a bool 'cancelling' bit and used the
following pattern under timer->lock to publish cancellation status.
lock(t->lock);
t->cancelling = true;
mb();
if (cur->cancelling)
return -EDEADLK;
unlock(t->lock);
hrtimer_cancel(t->timer);
t->cancelling = false;
The store outside the critical section could overwrite a parallel
requests t->cancelling assignment to true, to ensure the parallely
executing callback observes its cancellation status.
It would be necessary to clear this cancelling bit once hrtimer_cancel
is done, but lack of serialization introduced races. Another option was
explored where bpf_timer_start would clear the bit when (re)starting the
timer under timer->lock. This would ensure serialized access to the
cancelling bit, but may allow it to be cleared before in-flight
hrtimer_cancel has finished executing, such that lockups can occur
again.
Thus, we choose an atomic counter to keep track of all outstanding
cancellation requests and use it to prevent lockups in case callbacks
attempt to cancel each other while executing in parallel. |
