Description

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

net: use a bounce buffer for copying skb->mark

syzbot found arm64 builds would crash in sock_recv_mark()
when CONFIG_HARDENED_USERCOPY=y

x86 and powerpc are not detecting the issue because
they define user_access_begin.
This will be handled in a different patch,
because a check_object_size() is missing.

Only data from skb->cb[] can be copied directly to/from user space,
as explained in commit 79a8a642bf05 ("net: Whitelist
the skbuff_head_cache "cb" field")

syzbot report was:
usercopy: Kernel memory exposure attempt detected from SLUB object 'skbuff_head_cache' (offset 168, size 4)!
------------[ cut here ]------------
kernel BUG at mm/usercopy.c:102 !
Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 4410 Comm: syz-executor533 Not tainted 6.2.0-rc7-syzkaller-17907-g2d3827b3f393 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : usercopy_abort+0x90/0x94 mm/usercopy.c:90
lr : usercopy_abort+0x90/0x94 mm/usercopy.c:90
sp : ffff80000fb9b9a0
x29: ffff80000fb9b9b0 x28: ffff0000c6073400 x27: 0000000020001a00
x26: 0000000000000014 x25: ffff80000cf52000 x24: fffffc0000000000
x23: 05ffc00000000200 x22: fffffc000324bf80 x21: ffff0000c92fe1a8
x20: 0000000000000001 x19: 0000000000000004 x18: 0000000000000000
x17: 656a626f2042554c x16: ffff0000c6073dd0 x15: ffff80...

Classification

CVE ID: CVE-2023-52701

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.04% (probability of being exploited)

EPSS Percentile: 11.48% (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/863a7de987f02a901bf215509276a7de0370e0f9
https://git.kernel.org/stable/c/2558b8039d059342197610498c8749ad294adee5

Timeline