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Map iterator ctx->key and ctx->value are PTR_TO_BUF | PTR_MAYBE_NULL. On stop callbacks these are NULL, causing a kernel NULL dereference. Add a type_may_be_null() guard to the PTR_TO_BUF branch, matching the existing PTR_TO_BTF_ID pattern. BUG: kernel NULL pointer dereference, address: 0000000000000000 Oops: Oops: 0000 [#1] SMP KASAN NOPTI RIP: 0010:bpf_prog_5f0e2be830ac3243_null_deref_iter+0x10/0x25 Call Trace: bpf_iter_run_prog+0x1c2/0x2e0 __bpf_hash_map_seq_show+0x120/0x180 bpf_seq_read+0x29c/0x530 vfs_read+0x179/0x930 ksys_read+0xef/0x1c0 do_syscall_64+0xe0/0x1290 entry_SYSCALL_64_after_hwframe+0x76/0x7e Kernel panic - not syncing: Fatal exception Fixes: 20b2aff4bc15 ("bpf: Introduce MEM_RDONLY flag") Signed-off-by: Qi Tang --- kernel/bpf/verifier.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 937c9adf1b3d..17850836943b 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7905,7 +7905,8 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn } else if (reg->type == CONST_PTR_TO_MAP) { err = check_ptr_to_map_access(env, regs, regno, off, size, t, value_regno); - } else if (base_type(reg->type) == PTR_TO_BUF) { + } else if (base_type(reg->type) == PTR_TO_BUF && + !type_may_be_null(reg->type)) { bool rdonly_mem = type_is_rdonly_mem(reg->type); u32 *max_access; -- 2.43.0