CVE-2021-47335Medium· 5.5▾ SunlitIn the Linux kernel, the following vulnerability has been resolved: f2fs: fix to avoid racing on fsync_entry_slab by multi filesystem instances As syzbot reported, there is an use-after-free issue during f2fs recovery: Use-after-free …
▾ Sunlit zone — Low / medium · no exploitation signal
impact 30.3 · likelihood 0 · exploitation 0
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Exploit-prediction probability, daily snapshots since Aug 11.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
Last analysed / modified upstream
0.2%
In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix to avoid racing on fsync_entry_slab by multi filesystem instances
As syzbot reported, there is an use-after-free issue during f2fs recovery:
Use-after-free write at 0xffff88823bc16040 (in kfence-#10): kmem_cache_destroy+0x1f/0x120 mm/slab_common.c:486 f2fs_recover_fsync_data+0x75b0/0x8380 fs/f2fs/recovery.c:869 f2fs_fill_super+0x9393/0xa420 fs/f2fs/super.c:3945 mount_bdev+0x26c/0x3a0 fs/super.c:1367 legacy_get_tree+0xea/0x180 fs/fs_context.c:592 vfs_get_tree+0x86/0x270 fs/super.c:1497 do_new_mount fs/namespace.c:2905 [inline] path_mount+0x196f/0x2be0 fs/namespace.c:3235 do_mount fs/namespace.c:3248 [inline] __do_sys_mount fs/namespace.c:3456 [inline] __se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3433 do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae
The root cause is multi f2fs filesystem instances can race on accessing global fsync_entry_slab pointer, result in use-after-free issue of slab cache, fixes to init/destroy this slab cache only once during module init/destroy procedure to avoid this issue.
linux_kernel < 5.10.51linux_kernel >= 5.11, < 5.12.18linux_kernel >= 5.13, < 5.13.3Upgrade past the affected range:
linux_kernel 5.13.3Connected by shared product, vendor, weakness, or advisory.
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