cbcvebase.
CVE-2024-42305
published 2024-08-17

CVE-2024-42305: In the Linux kernel, the following vulnerability has been resolved: ext4: check dot and dotdot of dx_root before making dir indexed Syzbot reports a issue as…

PriorityP421medium5.5CVSS 3.1
AVLACLPRLUINSUCNINAH
EPSS
0.22%
13.2th percentile
In the Linux kernel, the following vulnerability has been resolved: ext4: check dot and dotdot of dx_root before making dir indexed Syzbot reports a issue as follows: BUG: unable to handle page fault for address: ffffed11022e24fe PGD 23ffee067 P4D 23ffee067 PUD 0 Oops: Oops: 0000 [#1] PREEMPT SMP KASAN PTI CPU: 0 PID: 5079 Comm: syz-executor306 Not tainted 6.10.0-rc5-g55027e689933 #0 Call Trace: make_indexed_dir+0xdaf/0x13c0 fs/ext4/namei.c:2341 ext4_add_entry+0x222a/0x25d0 fs/ext4/namei.c:2451 ext4_rename fs/ext4/namei.c:3936 [inline] ext4_rename2+0x26e5/0x4370 fs/ext4/namei.c:4214 [...] The immediate cause of this problem is that there is only one valid dentry for the block to be split during do_split, so split==0 results in out of bounds accesses to the map triggering the issue. do_split unsigned split dx_make_map count = 1 split = count/2 = 0; continued = hash2 == map[split - 1].hash; ---> map[4294967295] The maximum length of a filename is 255 and the minimum block size is 1024, so it is always guaranteed that the number of entries is greater than or equal to 2 when do_split() is called. But syzbot's crafted image has no dot and dotdot in dir, and the dentry distribution in dirblock is as follows: bus dentry1 hole dentry2 free |xx--|xx-------------|...............|xx-------------|...............| 0 12 (8+248)=256 268 256 524 (8+256)=264 788 236 1024 So when renaming dentry1 increases its name_len length by 1, neither hole nor free is sufficient to hold the new dentry, and make_indexed_dir() is called. In make_indexed_dir() it is assumed that the first two entries of the dirblock must be dot and dotdot, so bus and dentry1 are left in dx_root because they are treated as dot and dotdot, and only dentry2 is moved to the new leaf block. That's why count is equal to 1. Therefore add the ext4_check_dx_root() helper function to add more sanity checks to dot and dotdot before starting the conversion to avoid the above issue.

Affected

26 ranges· showing 25
VendorProductVersion rangeFixed in
debianlinux< linux 6.1.106-1 (bookworm)linux 6.1.106-1 (bookworm)
debianlinux-6.1< linux 6.1.106-1 (bookworm)linux 6.1.106-1 (bookworm)
linuxlinux
linuxlinux>= ac27a0ec112a089f1a5102bc8dffc79c8c815571 < b80575ffa98b5bb3a5d4d392bfe4c2e03e9557dbb80575ffa98b5bb3a5d4d392bfe4c2e03e9557db
linuxlinux>= ac27a0ec112a089f1a5102bc8dffc79c8c815571 < 19e13b4d7f0303186fcc891aba8d0de7c8fdbda819e13b4d7f0303186fcc891aba8d0de7c8fdbda8
linuxlinux>= ac27a0ec112a089f1a5102bc8dffc79c8c815571 < 42d420517072028fb0eb852c358056b7717ba5aa42d420517072028fb0eb852c358056b7717ba5aa
linuxlinux>= ac27a0ec112a089f1a5102bc8dffc79c8c815571 < 8afe06ed3be7a874b3cd82ef5f8959aca8d6429a8afe06ed3be7a874b3cd82ef5f8959aca8d6429a
linuxlinux>= ac27a0ec112a089f1a5102bc8dffc79c8c815571 < abb411ac991810c0bcbe51c2e76d2502bf611b5cabb411ac991810c0bcbe51c2e76d2502bf611b5c
linuxlinux>= ac27a0ec112a089f1a5102bc8dffc79c8c815571 < 9d241b7a39af192d1bb422714a458982c7cc67a29d241b7a39af192d1bb422714a458982c7cc67a2
linuxlinux>= ac27a0ec112a089f1a5102bc8dffc79c8c815571 < cdd345321699042ece4a9d2e70754d2397d378c5cdd345321699042ece4a9d2e70754d2397d378c5
linuxlinux>= ac27a0ec112a089f1a5102bc8dffc79c8c815571 < 50ea741def587a64e08879ce6c6a30131f7111e750ea741def587a64e08879ce6c6a30131f7111e7
linuxlinux_kernel
linuxlinux_kernel>= 0 < 5.10.226-15.10.226-1
linuxlinux_kernel>= 0 < 6.1.106-16.1.106-1
linuxlinux_kernel>= 0 < 6.10.3-16.10.3-1
linuxlinux_kernel>= 0 < 6.10.3-16.10.3-1
linuxlinux_kernel>= 0 < 5.4.0-200.2205.4.0-200.220
linuxlinux_kernel>= 0 < 5.15.0-125.1355.15.0-125.135
linuxlinux_kernel>= 0 < 6.8.0-50.516.8.0-50.51
linuxlinux_kernel>= 2.6.20 < 4.19.3204.19.320
linuxlinux_kernel>= 4.20 < 5.4.2825.4.282
linuxlinux_kernel>= 5.11 < 5.15.1655.15.165
linuxlinux_kernel>= 5.16 < 6.1.1036.1.103
linuxlinux_kernel>= 5.5 < 5.10.2245.10.224
linuxlinux_kernel>= 6.2 < 6.6.446.6.44

CVSS provenance

nvdv3.15.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
osv8.8HIGH
vendor_ubuntu8.8HIGH
vendor_debian5.5MEDIUM
vendor_redhat5.5MEDIUM
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