Description

In the Linux kernel, the following vulnerability has been resolved:

llc: make llc_ui_sendmsg() more robust against bonding changes

syzbot was able to trick llc_ui_sendmsg(), allocating an skb with no
headroom, but subsequently trying to push 14 bytes of Ethernet header [1]

Like some others, llc_ui_sendmsg() releases the socket lock before
calling sock_alloc_send_skb().
Then it acquires it again, but does not redo all the sanity checks
that were performed.

This fix:

- Uses LL_RESERVED_SPACE() to reserve space.
- Check all conditions again after socket lock is held again.
- Do not account Ethernet header for mtu limitation.

[1]

skbuff: skb_under_panic: text:ffff800088baa334 len:1514 put:14 head:ffff0000c9c37000 data:ffff0000c9c36ff2 tail:0x5dc end:0x6c0 dev:bond0

kernel BUG at net/core/skbuff.c:193 !
Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 6875 Comm: syz-executor.0 Not tainted 6.7.0-rc8-syzkaller-00101-g0802e17d9aca-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : skb_panic net/core/skbuff.c:189 [inline]
pc : skb_under_panic+0x13c/0x140 net/core/skbuff.c:203
lr : skb_panic net/core/skbuff.c:189 [inline]
lr : skb_under_panic+0x13c/0x140 net/core/skbuff.c:203
sp : ffff800096f97000
x29: ffff800096f97010 x28: ffff80008cc8d668 x27: dfff800000000000
x26: ffff0000cb970c90 x25: 00000000000005dc x24: f...

Classification

CVE ID: CVE-2024-26636

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.04% (probability of being exploited)

EPSS Percentile: 15.26% (scored less or equal to compared to others)

EPSS Date: 2025-02-04 (when was this score calculated)

References

https://git.kernel.org/stable/c/84e9d10419f6f4f3f3cd8f9aaf44a48719aa4b1b
https://git.kernel.org/stable/c/b643d0defcbacd7fe548bc65c3e4e6f17dc5eb2d
https://git.kernel.org/stable/c/04f2a74b562f3a7498be0399309669f342793d8c
https://git.kernel.org/stable/c/c22044270da68881074fda81a7d34812726cb249
https://git.kernel.org/stable/c/6d53b813ff8b177f86f149c2f744442681f720e4
https://git.kernel.org/stable/c/cafd3ad3fe03ef4d6632747be9ee15dc0029db4b
https://git.kernel.org/stable/c/c451c008f563d56d5e676c9dcafae565fcad84bb
https://git.kernel.org/stable/c/dad555c816a50c6a6a8a86be1f9177673918c647

Timeline