CVE-2024-42161 Information

Description

In the Linux kernel the following vulnerability has been resolved:

bpf: Avoid uninitialized value in BPF_CORE_READ_BITFIELD

[Changes from V1:

• Use a default branch in the switch statement to initialize `val’.]

GCC warns that `val’ may be used uninitialized in the BPF_CRE_READ_BITFIELD macro defined in bpf_core_read.h as:

[...]
unsigned long long val;						      \
[...]								      \
switch (__CORE_RELO(s field BYTE_SIZE)) 			      \
case 1: val = (const unsigned char )p; break;			      \
case 2: val = (const unsigned short )p; break;		      \
case 4: val = (const unsigned int )p; break;			      \
case 8: val = (const unsigned long long )p; break;		      \
           							      \
[...]
val;								      \
								      \

This patch adds a default entry in the switch statement that sets `val’ to zero in order to avoid the warning and random values to be used in case __builtin_preserve_field_info returns unexpected values for BPF_FIELD_BYTE_SIZE.

Tested in bpf-next master. No regressions.

Reference

https://git.kernel.org/stable/c/b694989bb13ed5f166e633faa1eb0f21c6d261a6 https://git.kernel.org/stable/c/3364c2ed1c241989847f19cf83e3db903ce689e3 https://git.kernel.org/stable/c/a21d76bd0b0d39518e9a4c19f6cf7c042a974aff https://git.kernel.org/stable/c/7e5471b5efebc30dd0bc035cda86693a5c73d45f https://git.kernel.org/stable/c/ff941a8449e712eaf7efca1a13bfb9afd3d99fc2 https://git.kernel.org/stable/c/009367099eb61a4fc2af44d4eb06b6b4de7de6db