- Description
- In the Linux kernel, the following vulnerability has been resolved: io_uring/rw: fix missing NOWAIT check for O_DIRECT start write When io_uring starts a write, it'll call kiocb_start_write() to bump the super block rwsem, preventing any freezes from happening while that write is in-flight. The freeze side will grab that rwsem for writing, excluding any new writers from happening and waiting for existing writes to finish. But io_uring unconditionally uses kiocb_start_write(), which will block if someone is currently attempting to freeze the mount point. This causes a deadlock where freeze is waiting for previous writes to complete, but the previous writes cannot complete, as the task that is supposed to complete them is blocked waiting on starting a new write. This results in the following stuck trace showing that dependency with the write blocked starting a new write: task:fio state:D stack:0 pid:886 tgid:886 ppid:876 Call trace: __switch_to+0x1d8/0x348 __schedule+0x8e8/0x2248 schedule+0x110/0x3f0 percpu_rwsem_wait+0x1e8/0x3f8 __percpu_down_read+0xe8/0x500 io_write+0xbb8/0xff8 io_issue_sqe+0x10c/0x1020 io_submit_sqes+0x614/0x2110 __arm64_sys_io_uring_enter+0x524/0x1038 invoke_syscall+0x74/0x268 el0_svc_common.constprop.0+0x160/0x238 do_el0_svc+0x44/0x60 el0_svc+0x44/0xb0 el0t_64_sync_handler+0x118/0x128 el0t_64_sync+0x168/0x170 INFO: task fsfreeze:7364 blocked for more than 15 seconds. Not tainted 6.12.0-rc5-00063-g76aaf945701c #7963 with the attempting freezer stuck trying to grab the rwsem: task:fsfreeze state:D stack:0 pid:7364 tgid:7364 ppid:995 Call trace: __switch_to+0x1d8/0x348 __schedule+0x8e8/0x2248 schedule+0x110/0x3f0 percpu_down_write+0x2b0/0x680 freeze_super+0x248/0x8a8 do_vfs_ioctl+0x149c/0x1b18 __arm64_sys_ioctl+0xd0/0x1a0 invoke_syscall+0x74/0x268 el0_svc_common.constprop.0+0x160/0x238 do_el0_svc+0x44/0x60 el0_svc+0x44/0xb0 el0t_64_sync_handler+0x118/0x128 el0t_64_sync+0x168/0x170 Fix this by having the io_uring side honor IOCB_NOWAIT, and only attempt a blocking grab of the super block rwsem if it isn't set. For normal issue where IOCB_NOWAIT would always be set, this returns -EAGAIN which will have io_uring core issue a blocking attempt of the write. That will in turn also get completions run, ensuring forward progress. Since freezing requires CAP_SYS_ADMIN in the first place, this isn't something that can be triggered by a regular user.
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
- NVD status
- Analyzed
CVSS 3.1
- Type
- Primary
- Base score
- 4.4
- Impact score
- 3.6
- Exploitability score
- 0.8
- Vector string
- CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
- Severity
- MEDIUM
- nvd@nist.gov
- CWE-667
- Hype score
- Not currently trending
[
{
"nodes": [
{
"negate": false,
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "E49CED4C-F21B-4CBC-893C-F59CC2CDE34B",
"versionEndExcluding": "5.10.230"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "88812664-4296-42AC-AE0F-ED71086C1BB1",
"versionEndExcluding": "5.15.172",
"versionStartIncluding": "5.11"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "43EFDC15-E4D4-4F1E-B70D-62F0854BFDF3",
"versionEndExcluding": "6.1.116",
"versionStartIncluding": "5.16"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "75088E5E-2400-4D20-915F-7A65C55D9CCD",
"versionEndExcluding": "6.6.60",
"versionStartIncluding": "6.2"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "E96F53A4-5E87-4A70-BD9A-BC327828D57F",
"versionEndExcluding": "6.11.7",
"versionStartIncluding": "6.7"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:6.12:rc1:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "7F361E1D-580F-4A2D-A509-7615F73167A1"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:6.12:rc2:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "925478D0-3E3D-4E6F-ACD5-09F28D5DF82C"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:6.12:rc3:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "3C95E234-D335-4B6C-96BF-E2CEBD8654ED"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:6.12:rc4:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "E0F717D8-3014-4F84-8086-0124B2111379"
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:6.12:rc5:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "24DBE6C7-2AAE-4818-AED2-E131F153D2FA"
}
],
"operator": "OR"
}
]
}
]