Description

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

net/sched: act_skbmod: prevent kernel-infoleak

syzbot found that tcf_skbmod_dump() was copying four bytes
from kernel stack to user space [1].

The issue here is that 'struct tc_skbmod' has a four bytes hole.

We need to clear the structure before filling fields.

[1]
BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline]
BUG: KMSAN: kernel-infoleak in copy_to_user_iter lib/iov_iter.c:24 [inline]
BUG: KMSAN: kernel-infoleak in iterate_ubuf include/linux/iov_iter.h:29 [inline]
BUG: KMSAN: kernel-infoleak in iterate_and_advance2 include/linux/iov_iter.h:245 [inline]
BUG: KMSAN: kernel-infoleak in iterate_and_advance include/linux/iov_iter.h:271 [inline]
BUG: KMSAN: kernel-infoleak in _copy_to_iter+0x366/0x2520 lib/iov_iter.c:185
instrument_copy_to_user include/linux/instrumented.h:114 [inline]
copy_to_user_iter lib/iov_iter.c:24 [inline]
iterate_ubuf include/linux/iov_iter.h:29 [inline]
iterate_and_advance2 include/linux/iov_iter.h:245 [inline]
iterate_and_advance include/linux/iov_iter.h:271 [inline]
_copy_to_iter+0x366/0x2520 lib/iov_iter.c:185
copy_to_iter include/linux/uio.h:196 [inline]
simple_copy_to_iter net/core/datagram.c:532 [inline]
__skb_datagram_iter+0x185/0x1000 net/core/datagram.c:420
skb_copy_datagram_iter+0x5c/0x200 net/core/datagram.c:546
skb_copy_datagram_msg include/linux/skbuff.h:4050 [inline]
netlink_recvmsg+0x432/...

Classification

CVE ID: CVE-2024-35893

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/f190a4aa03cbd518bd9c62a66e1233984f5fd2ec
https://git.kernel.org/stable/c/f356eb2fb567e0931143ac1769ac802d3b3e2077
https://git.kernel.org/stable/c/5e45dc4408857305f4685abfd7a528a1e58b51b5
https://git.kernel.org/stable/c/a097fc199ab5f4b5392c5144034c0d2148b55a14
https://git.kernel.org/stable/c/55d3fe7b2b7bc354e7cbc1f7b8f98a29ccd5a366
https://git.kernel.org/stable/c/729ad2ac2a2cdc9f4a4bdfd40bfd276e6bc33924
https://git.kernel.org/stable/c/7bb2c7103d8c13b06a57bf997b8cdbe93cd7283c
https://git.kernel.org/stable/c/d313eb8b77557a6d5855f42d2234bd592c7b50dd

Timeline