Description
In the Linux kernel, the following vulnerability has been resolved: bpf: Reject >8 byte return values on return-reading trampoline paths btf_distill_func_proto() builds the function model used for the fentry/fexit/fmod_ret/fsession trampolines and struct_ops. It has accepted a 16-byte __int128 return value since the trampoline was introduced: __get_type_size() returns the integer's type size, and the return-type check only rejected ret < 0. But the BPF trampoline preserves only 8 bytes of the return value (RAX on x86, i.e. R0). For an attach type that reads the target's return value the second half (RDX / R3) is neither saved nor restored, so a program attached to a function returning a 16-byte value corrupts the value seen by the real caller and itself observes only half of it. struct_ops trampolines have the same limitation. This affects the attach types that read the target's return value: fexit, fmod_ret and fsession (plus the _multi variants of fexit and fsession), and struct_ops. fentry/fentry_multi run before the target returns and are unaffected. Reject a >8 byte return value for these attach types in bpf_check_attach_target() and bpf_check_attach_btf_id_multi(), and for struct_ops in bpf_struct_ops_desc_init().
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
fec56f5890d93fc2ed74166c397dc186b1c25951 to < de54ba33690d2dd3c4aa686c9693505644285b0baffectedfec56f5890d93fc2ed74166c397dc186b1c25951 to < 9a9e902bd0556052534641f7d5f868c6dc4b84aeaffectedfec56f5890d93fc2ed74166c397dc186b1c25951 to < d36ac53fc83baf843c51b7afd6d2471f36b713d8affectedfec56f5890d93fc2ed74166c397dc186b1c25951 to < c48796aa6c392cde93946e5d5a9a1f1b1cf72febaffected
Linux Linux
Default version status: affected
5.5affected0 to < 5.5unaffected6.12.114 to ≤ 6.12.*unaffected6.18.57 to ≤ 6.18.*unaffected7.2.6 to ≤ 7.2.*unaffected7.3 to ≤ *unaffected