Out-of-bounds Read Affecting kernel-tools package, versions *
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Test your applications- Snyk ID SNYK-RHEL8-KERNELTOOLS-7758147
- published 21 Aug 2024
- disclosed 17 Aug 2024
Introduced: 17 Aug 2024
CVE-2024-42305 Open this link in a new tabHow to fix?
There is no fixed version for RHEL:8 kernel-tools.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-tools package and not the kernel-tools package as distributed by RHEL.
See How to fix? for RHEL:8 relevant fixed versions and status.
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: <TASK> 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.
References
- https://access.redhat.com/security/cve/CVE-2024-42305
- https://git.kernel.org/stable/c/50ea741def587a64e08879ce6c6a30131f7111e7
- https://git.kernel.org/stable/c/9d241b7a39af192d1bb422714a458982c7cc67a2
- https://git.kernel.org/stable/c/abb411ac991810c0bcbe51c2e76d2502bf611b5c
- https://git.kernel.org/stable/c/cdd345321699042ece4a9d2e70754d2397d378c5
- https://git.kernel.org/stable/c/19e13b4d7f0303186fcc891aba8d0de7c8fdbda8
- https://git.kernel.org/stable/c/42d420517072028fb0eb852c358056b7717ba5aa
- https://git.kernel.org/stable/c/8afe06ed3be7a874b3cd82ef5f8959aca8d6429a
- https://git.kernel.org/stable/c/b80575ffa98b5bb3a5d4d392bfe4c2e03e9557db