CVE-2026-93125bpf: Reject rdonly/rdwr_buf_size kfunc arguments that exceed u32 max

Official description

In the Linux kernel, the following vulnerability has been resolved: bpf: Reject rdonly/rdwr_buf_size kfunc arguments that exceed u32 max check_kfunc_args() detects a kfunc argument named rdonly_buf_size or rdwr_buf_size and stores reg->var_off.value into meta->r0_size, a u64, and does not bound it. check_kfunc_call() later copies that value into the returned register's mem_size field: meta->r0_size = reg->var_off.value; ... regs[BPF_REG_0].mem_size = meta.r0_size; regs[BPF_REG_0].mem_size is u32. A constant whose upper 32 bits are set gets truncated instead of causing a load-time rejection, so the verifier records a PTR_TO_MEM register with an approximately 4 GiB mem_size for whatever allocation the kfunc returned. A later access check against that register uses the truncated, wrong bound. Reject rdonly_buf_size/rdwr_buf_size values that exceed U32_MAX at the point meta->r0_size is set.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/00bb52be60da16cd5ead4eb9f8ddc9a66d003ff2
• https://git.kernel.org/stable/c/2147065d3a4e1d5d42ae553fef165f17ec5e0e79
• https://git.kernel.org/stable/c/b6ac0b5732047d43172b9dfbe6b57b9b8de303c2
• https://git.kernel.org/stable/c/93a20b14f8627b2d3486e3ec1d3f2e7275a506ec
• https://git.kernel.org/stable/c/56a3846830ac95a472297d0cbba75cbff29540bb
• https://git.kernel.org/stable/c/2aaf67f0516fde29620d0edfc29c01b9ea7ad430