Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge branch 'bpf-fix-null-deref-when-storing-scalar-into-kptr-slot'
Mykyta Yatsenko says:
====================
bpf: Fix NULL deref when storing scalar into kptr slot
map_kptr_match_type() accesses reg->btf before confirming the register
is PTR_TO_BTF_ID. A scalar store into a kptr slot has no btf, causing
a NULL pointer dereference. Guard base_type() first.
Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
====================
Link: https://patch.msgid.link/20260416-kptr_crash-v1-0-5589356584b4@meta.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
+19
-1
+4
-1
kernel/bpf/verifier.c
+4
-1
kernel/bpf/verifier.c
···
4549
4549
int perm_flags;
4550
4550
const char *reg_name = "";
4551
4551
4552
+
if (base_type(reg->type) != PTR_TO_BTF_ID)
4553
+
goto bad_type;
4554
+
4552
4555
if (btf_is_kernel(reg->btf)) {
4553
4556
perm_flags = PTR_MAYBE_NULL | PTR_TRUSTED | MEM_RCU;
4554
4557
···
4564
4561
perm_flags |= MEM_PERCPU;
4565
4562
}
4566
4563
4567
-
if (base_type(reg->type) != PTR_TO_BTF_ID || (type_flag(reg->type) & ~perm_flags))
4564
+
if (type_flag(reg->type) & ~perm_flags)
4568
4565
goto bad_type;
4569
4566
4570
4567
/* We need to verify reg->type and reg->btf, before accessing reg->btf */
+15
tools/testing/selftests/bpf/progs/map_kptr_fail.c
+15
tools/testing/selftests/bpf/progs/map_kptr_fail.c
···
385
385
return 0;
386
386
}
387
387
388
+
SEC("?tc")
389
+
__failure __msg("invalid kptr access, R")
390
+
int reject_scalar_store_to_kptr(struct __sk_buff *ctx)
391
+
{
392
+
struct map_value *v;
393
+
int key = 0;
394
+
395
+
v = bpf_map_lookup_elem(&array_map, &key);
396
+
if (!v)
397
+
return 0;
398
+
399
+
*(volatile u64 *)&v->unref_ptr = 0xBADC0DE;
400
+
return 0;
401
+
}
402
+
388
403
char _license[] SEC("license") = "GPL";