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bpf: mark a NULL call argument precise

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check_func_arg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.

check_helper_call() enforces second parameter of the
bpf_get_local_storage() to be zero, w/o marking the underlying scalar
register precise. Hence a checkpoint created on such a path would
prune against arbitrary scalar value.

Grouping these two into one patch, as they share the same fixes tag.

Fixes: b5dc0163d8 ("bpf: precise scalar_value tracking")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-1-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Eduard Zingerman
2026-09-04 18:17:29 -07:00
committed by Alexei Starovoitov
parent 519f858317
commit 1a3a10b030
2 changed files with 14 additions and 7 deletions
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tools/testing/selftests/bpf/progs/verifier_subprog_precision.c
+6 -6
View File
@@ -287,9 +287,9 @@ __msg("17: (b7) r0 = 0")
__msg("18: (95) exit")
__msg("returning from callee:")
__msg("to caller at 9:")
__msg("frame 0: propagating r1,r4")
__msg("frame 0: propagating r1,r3,r4")
__msg("mark_precise: frame0: last_idx 9 first_idx 9 subseq_idx -1")
__msg("mark_precise: frame0: regs=r1,r4 stack= before 18: (95) exit")
__msg("mark_precise: frame0: regs=r1,r3,r4 stack= before 18: (95) exit")
__msg("from 18 to 9: safe")
__naked int callback_result_precise(void)
{
@@ -419,9 +419,9 @@ __msg("to caller at 9:")
/* r1, r4 are always precise for bpf_loop(),
* r6 was marked before backtracking to callback body.
*/
__msg("frame 0: propagating r1,r4,r6")
__msg("frame 0: propagating r1,r3,r4,r6")
__msg("mark_precise: frame0: last_idx 9 first_idx 9 subseq_idx -1")
__msg("mark_precise: frame0: regs=r1,r4,r6 stack= before 16: (95) exit")
__msg("mark_precise: frame0: regs=r1,r3,r4,r6 stack= before 16: (95) exit")
__msg("mark_precise: frame1: regs= stack= before 15: (b7) r0 = 0")
__msg("mark_precise: frame1: regs= stack= before 9: (85) call bpf_loop")
__msg("mark_precise: frame0: parent state regs= stack=:")
@@ -575,9 +575,9 @@ __msg("to caller at 10:")
/* r1, r4 are always precise for bpf_loop(),
* fp-8 was marked before backtracking to callback body.
*/
__msg("frame 0: propagating r1,r4,fp-8")
__msg("frame 0: propagating r1,r3,r4,fp-8")
__msg("mark_precise: frame0: last_idx 10 first_idx 10 subseq_idx -1")
__msg("mark_precise: frame0: regs=r1,r4 stack=-8 before 18: (95) exit")
__msg("mark_precise: frame0: regs=r1,r3,r4 stack=-8 before 18: (95) exit")
__msg("mark_precise: frame1: regs= stack= before 17: (b7) r0 = 0")
__msg("mark_precise: frame1: regs= stack= before 10: (85) call bpf_loop#181")
__msg("mark_precise: frame0: parent state regs= stack=:")