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| author | Alexei Starovoitov <ast@kernel.org> | 2025-10-01 13:53:20 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2025-10-01 13:55:08 -0700 |
| commit | a1aca22d264cdca5b20934a2413951ea7d73c594 (patch) | |
| tree | 761496156250d09e0e9d9294da0b21752c461878 | |
| parent | 0c342bfc9949dffeaa83ebdde3b4b0ce59009348 (diff) | |
| parent | 8709c1685220e766d4d9420f96b1e8ed3175f526 (diff) | |
Merge branch 'bpf-fix-verifier-crash-on-bpf_neg-with-pointer-register'
Brahmajit Das says:
====================
bpf: Fix verifier crash on BPF_NEG with pointer register
This patch fixes a crash in the BPF verifier triggered when the BPF_NEG
operation is applied to a pointer-typed register. The verifier now
checks that the destination register is not a pointer before performing
the operation.
Tested with syzkaller reproducer and new BPF sefltest.
Closes: https://syzkaller.appspot.com/bug?extid=d36d5ae81e1b0a53ef58
Changes v4:
Cleaning up, instead of using __is_pointer_value it's further
simplified by checking if regs[insn->dst_reg].type of SCALAR_VALUE
Link:
Changes in v3:
using __is_pointer_value to check if register if of pointer type
Link: https://lore.kernel.org/all/20251001095613.267475-1-listout@listout.xyz/
Changes in v2:
Checking if reg->map_ptr is NULL in bpf/log.c but with cleaner approach
(wrong approach)
Link: https://lore.kernel.org/all/20250923174738.1713751-1-listout@listout.xyz/
Changes in v1:
Checking if reg->map_ptr is NULL in bpf/log.c (wrong approach)
Link: https://lore.kernel.org/all/20250923164144.1573636-1-listout@listout.xyz/
====================
Link: https://patch.msgid.link/20251001191739.2323644-1-listout@listout.xyz
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
| -rw-r--r-- | kernel/bpf/verifier.c | 3 | ||||
| -rw-r--r-- | tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c | 18 |
2 files changed, 20 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 73bba397672a..a5c52d53502a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -15645,7 +15645,8 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn) } /* check dest operand */ - if (opcode == BPF_NEG) { + if (opcode == BPF_NEG && + regs[insn->dst_reg].type == SCALAR_VALUE) { err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK); err = err ?: adjust_scalar_min_max_vals(env, insn, ®s[insn->dst_reg], diff --git a/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c b/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c index a9ab37d3b9e2..dcaab61a11a0 100644 --- a/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c +++ b/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c @@ -146,6 +146,24 @@ l0_%=: exit; \ : __clobber_all); } +SEC("socket") +__description("map_ptr illegal alu op, map_ptr = -map_ptr") +__failure __msg("R0 invalid mem access 'scalar'") +__failure_unpriv __msg_unpriv("R0 pointer arithmetic prohibited") +__flag(BPF_F_ANY_ALIGNMENT) +__naked void map_ptr_illegal_alu_op(void) +{ + asm volatile (" \ + r0 = %[map_hash_48b] ll; \ + r0 = -r0; \ + r1 = 22; \ + *(u64*)(r0 + 0) = r1; \ + exit; \ +" : + : __imm_addr(map_hash_48b) + : __clobber_all); +} + SEC("flow_dissector") __description("flow_keys illegal alu op with variable offset") __failure __msg("R7 pointer arithmetic on flow_keys prohibited") |