6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Emil Tsalapatis [ Upstream commit 4a4852376e3a2727ea40e61143d6d7c22bb6dfad ] Currently, the ctx access code reads the rx_queue_mapping field with either a 4-byte or 2-byte load. The rest of the bits in the register are marked known zero by the verifier. However, the emitted ctx access code places in the register on certain the special value (-1) using BPF_MOV_IMM64, which gets sign-extended to turn on all the bits in the register. By shifting this value right, the program ends up with a value at runtime above what the verifier assumes is possible. Fix this by ensuring the read value is as wide as the assumed size. Use MOV32 instructions instead of MOV64 instructions to keep the upper bits zero as assumed by the verifier. Also properly report the size of the destination variable (the bpf_sock field, 4 bytes) instead of the source (the socket field, 2 bytes). Fixes: c3c16f2ea6d2 ("bpf: Add rx_queue_mapping to bpf_sock") Reported-by: Nicholas Carlini Suggested-by: Nicholas Carlini Signed-off-by: Emil Tsalapatis Signed-off-by: Alexei Starovoitov Reviewed-by: Jiayuan Chen Link: https://patch.msgid.link/20260922172028.6269-4-emil@etsalapatis.com Signed-off-by: Sasha Levin --- net/core/filter.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index dea8dd48d4aa6..308b86abe4608 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -10247,11 +10247,12 @@ u32 bpf_sock_convert_ctx_access(enum bpf_access_type type, target_size)); *insn++ = BPF_JMP_IMM(BPF_JNE, si->dst_reg, NO_QUEUE_MAPPING, 1); - *insn++ = BPF_MOV64_IMM(si->dst_reg, -1); + *insn++ = BPF_MOV32_IMM(si->dst_reg, -1); #else - *insn++ = BPF_MOV64_IMM(si->dst_reg, -1); - *target_size = 2; + *insn++ = BPF_MOV32_IMM(si->dst_reg, -1); #endif + *target_size = sizeof_field(struct bpf_sock, rx_queue_mapping); + break; } -- 2.53.0