| Message ID | 5857040.2sfW0oRrdW@tauon.chronox.de (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Herbert Xu |
| Headers | show |
On Thu, Sep 21, 2017 at 10:16:53AM +0200, Stephan Mueller wrote: > The SGL is MAX_SGL_ENTS + 1 in size. The last SG entry is used for the > chaining and is properly updated with the sg_chain invocation. During > the filling-in of the initial SG entries, sg_mark_end is called for each > SG entry. This is appropriate as long as no additional SGL is chained > with the current SGL. However, when a new SGL is chained and the last > SG entry is updated with sg_chain, the last but one entry still contains > the end marker from the sg_mark_end. This end marker must be removed as > otherwise a walk of the chained SGLs will cause a NULL pointer > dereference at the last but one SG entry, because sg_next will return > NULL. > > The patch only applies to all kernels up to and including 4.13. The > patch 2d97591ef43d0587be22ad1b0d758d6df4999a0b added to 4.14-rc1 > introduced a complete new code base which addresses this bug in > a different way. Yet, that patch is too invasive for stable kernels > and was therefore not marked for stable. > > Fixes: 8ff590903d5fc ("crypto: algif_skcipher - User-space interface > for skcipher operations") > CC: <stable@vger.kernel.org> > CC: Herbert Xu <herbert@gondor.apana.org.au> > Signed-off-by: Stephan Mueller <smueller@chronox.de> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Thanks,
diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c index 43839b00fe6c..62449a8f14ce 100644 --- a/crypto/algif_skcipher.c +++ b/crypto/algif_skcipher.c @@ -139,8 +139,10 @@ static int skcipher_alloc_sgl(struct sock *sk) sg_init_table(sgl->sg, MAX_SGL_ENTS + 1); sgl->cur = 0; - if (sg) + if (sg) { sg_chain(sg, MAX_SGL_ENTS + 1, sgl->sg); + sg_unmark_end(sg + (MAX_SGL_ENTS - 1)); + } list_add_tail(&sgl->list, &ctx->tsgl); }
The SGL is MAX_SGL_ENTS + 1 in size. The last SG entry is used for the chaining and is properly updated with the sg_chain invocation. During the filling-in of the initial SG entries, sg_mark_end is called for each SG entry. This is appropriate as long as no additional SGL is chained with the current SGL. However, when a new SGL is chained and the last SG entry is updated with sg_chain, the last but one entry still contains the end marker from the sg_mark_end. This end marker must be removed as otherwise a walk of the chained SGLs will cause a NULL pointer dereference at the last but one SG entry, because sg_next will return NULL. The patch only applies to all kernels up to and including 4.13. The patch 2d97591ef43d0587be22ad1b0d758d6df4999a0b added to 4.14-rc1 introduced a complete new code base which addresses this bug in a different way. Yet, that patch is too invasive for stable kernels and was therefore not marked for stable. Fixes: 8ff590903d5fc ("crypto: algif_skcipher - User-space interface for skcipher operations") CC: <stable@vger.kernel.org> CC: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Stephan Mueller <smueller@chronox.de> --- crypto/algif_skcipher.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)