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crypto: af-alg - fix NULL pointer dereference in scatterwalk

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The AF_ALG interface fails to unmark the end of a Scatter/Gather List (SGL)
when chaining a new af_alg_tsgl structure. If a sendmsg() fills an SGL
exactly to MAX_SGL_ENTS, the last entry is marked as the end. A subsequent
sendmsg() allocates a new SGL and chains it, but fails to clear the end
marker on the previous SGL's last data entry.

This causes the crypto scatterwalk to hit a premature end, returning NULL
on sg_next() and leading to a kernel panic during dereference.

Fix this by explicitly unmarking the end of the previous SGL when
performing sg_chain() in af_alg_alloc_tsgl().

Fixes: 8ff590903d ("crypto: algif_skcipher - User-space interface for skcipher operations")
Signed-off-by: Norbert Szetei <norbert@doyensec.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Norbert Szetei
2026-03-25 18:26:13 +01:00
committed by Herbert Xu
parent 6d89f743e5
commit 62397b493e
1 changed files with 3 additions and 1 deletions
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4
crypto/af_alg.c
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@@ -623,8 +623,10 @@ static int af_alg_alloc_tsgl(struct sock *sk)
sg_init_table(sgl->sg, MAX_SGL_ENTS + 1);
sgl->cur = 0;
if (sg)
if (sg) {
sg_unmark_end(sg + MAX_SGL_ENTS - 1);
sg_chain(sg, MAX_SGL_ENTS + 1, sgl->sg);
}
list_add_tail(&sgl->list, &ctx->tsgl_list);
}