diff options
| author | Alexei Starovoitov <ast@kernel.org> | 2026-03-03 08:45:16 -0800 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2026-03-03 08:45:16 -0800 |
| commit | b0000448094892c9131e485b64be2d5ef62ab73b (patch) | |
| tree | 817e2fd77f8ec8431d18bea57b8ac8cdf76e6f32 /kernel | |
| parent | b1d6bd5462f1e16adb805ce293bd11e9d7c47e6c (diff) | |
| parent | f6312e71759ddb10b20fbdb9ee01b9546cabd4e3 (diff) | |
Merge branch 'allow-fixed-offsets-for-ptr_to_ctx'
Kumar Kartikeya Dwivedi says:
====================
Allow fixed offsets for PTR_TO_CTX
Enable pointer modification with constant offsets accumulated in the
register for PTR_TO_CTX for programs where it won't be rewritten. See
patches for details.
====================
Link: https://patch.msgid.link/20260227005725.1247305-1-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/verifier.c | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index fc4ccd1de569..34f89ed29c47 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7752,6 +7752,11 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn if (!err && value_regno >= 0 && (t == BPF_READ || rdonly_mem)) mark_reg_unknown(env, regs, value_regno); } else if (reg->type == PTR_TO_CTX) { + /* + * Program types that don't rewrite ctx accesses can safely + * dereference ctx pointers with fixed offsets. + */ + bool fixed_off_ok = !env->ops->convert_ctx_access; struct bpf_retval_range range; struct bpf_insn_access_aux info = { .reg_type = SCALAR_VALUE, @@ -7765,10 +7770,16 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn return -EACCES; } - err = check_ptr_off_reg(env, reg, regno); + err = __check_ptr_off_reg(env, reg, regno, fixed_off_ok); if (err < 0) return err; + /* + * Fold the register's constant offset into the insn offset so + * that is_valid_access() sees the true effective offset. + */ + if (fixed_off_ok) + off += reg->var_off.value; err = check_ctx_access(env, insn_idx, off, size, t, &info); if (err) verbose_linfo(env, insn_idx, "; "); |