skbmark_decode(), skbprio_decode() and skbtcindex_decode() read fixed-size
values from the TLV payload without validating its length.
A malformed IFE frame can declare a shorter payload, causing the decoders
to consume bytes beyond the declared metadata value:
[TLV type=IFE_META_SKBMARK len=4]
-> dlen == 0, but decode reads 4 bytes
The decoder may therefore set skb metadata from unintended input.
Validate the payload length before decoding and return -EINVAL for
invalid lengths. Read the values with get_unaligned_be32() and
get_unaligned_be16(), as TLV payloads are not guaranteed to be
aligned. Teach tcf_ife_decode() to log a decoder error separately
from an unknown metaid; both are counted as overlimits and decoding
continues with the remaining metadata.
The metadata length issue was found by an automated audit of the IFE
decode path at v6.18-rc7 and reproduced with a userspace sanitizer
model of the decode path. Compile-tested on x86_64 with defconfig and
NET_ACT_IFE=y: act_ife.o and the three act_meta_*.o build
warning-free.
Fixes: 084e2f6566 ("Support to encoding decoding skb mark on IFE action")
Fixes: 200e10f469 ("Support to encoding decoding skb prio on IFE action")
Fixes: 408fbc22ef ("net sched ife action: Introduce skb tcindex metadata encap decap")
Assisted-by: Hawkeye:GLM-5.3-flash
Assisted-by: Qoder:Qwen3.8-Max
Signed-off-by: Fang Xieyan <fangxy@xiaopeng.com>
Link: https://patch.msgid.link/20260921125441.81459-1-fangxy@xiaopeng.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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