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| author | Weiming Shi <bestswngs@gmail.com> | 2026-04-23 21:38:32 +0300 |
|---|---|---|
| committer | Martin KaFai Lau <martin.lau@kernel.org> | 2026-04-24 04:27:18 +0300 |
| commit | 1081de1accb2b224516cca7071122c59532d0b22 (patch) | |
| tree | 7322af30b97d42787efadbe9423f7cb3f89f912c | |
| parent | 6451d58a355642b612f2bf948ad39108c998ac2a (diff) | |
| download | linux-1081de1accb2b224516cca7071122c59532d0b22.tar.xz | |
bpf: Fix NULL pointer dereference in bpf_skb_fib_lookup()
When tot_len is not provided by the user, bpf_skb_fib_lookup()
resolves the FIB result's output device via dev_get_by_index_rcu()
to check skb forwardability and fill in mtu_result. The returned
pointer is dereferenced without a NULL check. If the device is
concurrently unregistered, dev_get_by_index_rcu() returns NULL and
is_skb_forwardable() crashes at dev->flags:
KASAN: null-ptr-deref in range
[0x00000000000000b0-0x00000000000000b7]
Call Trace:
is_skb_forwardable (include/linux/netdevice.h:4365)
bpf_skb_fib_lookup (net/core/filter.c:6446)
bpf_prog_test_run_skb (net/bpf/test_run.c)
__sys_bpf (kernel/bpf/syscall.c)
Add the missing NULL check, returning -ENODEV to be consistent
with how bpf_ipv4_fib_lookup() and bpf_ipv6_fib_lookup() handle
the same condition.
Fixes: 4f74fede40df ("bpf: Add mtu checking to FIB forwarding helper")
Reported-by: Xiang Mei <xmei5@asu.edu>
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Acked-by: Paul Chaignon <paul.chaignon@gmail.com>
Link: https://patch.msgid.link/20260423183831.1325480-2-bestswngs@gmail.com
| -rw-r--r-- | net/core/filter.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index 2914f5330310..bc96c18df4e0 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -6473,6 +6473,8 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb, * against MTU of FIB lookup resulting net_device */ dev = dev_get_by_index_rcu(net, params->ifindex); + if (unlikely(!dev)) + return -ENODEV; if (!is_skb_forwardable(dev, skb)) rc = BPF_FIB_LKUP_RET_FRAG_NEEDED; |