CVE-2024-49850

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

bpf: correctly handle malformed BPF_CORE_TYPE_ID_LOCAL relos

In case of malformed relocation record of kind BPF_CORE_TYPE_ID_LOCAL referencing a non-existing BTF type, function bpf_core_calc_relo_insn would cause a null pointer deference.

Fix this by adding a proper check upper in call stack, as malformed relocation records could be passed from user space.

Simplest reproducer is a program:

r0 = 0
exit

With a single relocation record:

.insn_off = 0,          /* patch first instruction */
.type_id = 100500,      /* this type id does not exist */
.access_str_off = 6,    /* offset of string 0 */
.kind = BPF_CORE_TYPE_ID_LOCAL,

See the link for original reproducer or next commit for a test case.

Weakness

A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/2288b54b96dcb55bedebcef3572bb8821fc5e708
• https://git.kernel.org/stable/c/3d2786d65aaa954ebd3fcc033ada433e10da21c4
• https://git.kernel.org/stable/c/584cd3ff792e1edbea20b2a7df55897159b0be3e
• https://git.kernel.org/stable/c/dc7ce14f00bcd50641f2110b7a32aa6552e0780f
• https://git.kernel.org/stable/c/e7e9c5b2dda29067332df2a85b0141a92b41f218