kernel/git/stable/linux.git/crypto/af_alg.c, branch linux-6.18.y

crypto: af_alg - Remove zero-copy support from skcipher and aead

2026-07-18T14:53:27+00:00

commit ffdd2bc378953b525aca61902534e753f1f8e734 upstream. The zero-copy support is one of the riskiest aspects of AF_ALG. It allows userspace to request cryptographic operations directly on pagecache pages of files like the 'su' binary. It also allows userspace to concurrently modify the memory which is being operated on, a recipe for TOCTOU vulnerabilities. While zero-copy support is more valuable in other areas of the kernel like the frequently used networking and file I/O code, it has far less value in AF_ALG, which is a niche UAPI. AF_ALG primarily just exists for backwards compatibility with a small set of userspace programs such as 'iwd' that haven't yet been fixed to use userspace crypto code. Originally AF_ALG was intended to be used to access hardware crypto accelerators. However, it isn't an efficient interface for that anyway, and it turned out to be rarely used in this way in practice. Thus, the risks of the zero-copy support in AF_ALG vastly outweigh its benefits. Let's just remove it. This commit removes it from the "skcipher" and "aead" algorithm types. "hash" will be handled separately. This is a soft break, not a hard break. Even after this commit, it still works to use splice() or sendfile() to transfer data to an AF_ALG request socket from a pipe or any file, respectively. What changes is just that the kernel now makes an internal, stable copy of the data before doing the crypto operation. So performance is slightly reduced, but the UAPI isn't broken. And, very importantly, it's much safer. Tested with libkcapi/test.sh. All its test cases still pass. I also verified that this would have prevented the copy.fail exploit as well. I also used a custom test program to verify that sendfile() still works. Fixes: 8ff590903d5f ("crypto: algif_skcipher - User-space interface for skcipher operations") Fixes: 400c40cf78da ("crypto: algif - add AEAD support") Reported-by: Taeyang Lee <0wn@theori.io> Link: https://copy.fail/ Reported-by: Feng Ning Closes: https://lore.kernel.org/r/afYcc-tZFwvZZo76@ans-MacBook-Pro.local Reviewed-by: Demi Marie Obenour Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman

crypto: af_alg - Cap AEAD AD length to 0x80000000

2026-05-23T11:07:15+00:00

commit e4c06479d7059888adf2f22bc1ebcf053bf691a2 upstream. In order to prevent arithmetic overflows when checking the TX buffer size, cap the associated data length to 0x80000000. Reported-by: Yiming Qian Fixes: 400c40cf78da ("crypto: algif - add AEAD support") Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman

crypto: af_alg - Fix page reassignment overflow in af_alg_pull_tsgl

2026-04-22T11:22:24+00:00

[ Upstream commit 31d00156e50ecad37f2cb6cbf04aaa9a260505ef ] When page reassignment was added to af_alg_pull_tsgl the original loop wasn't updated so it may try to reassign one more page than necessary. Add the check to the reassignment so that this does not happen. Also update the comment which still refers to the obsolete offset argument. Reported-by: syzbot+d23888375c2737c17ba5@syzkaller.appspotmail.com Fixes: e870456d8e7c ("crypto: algif_skcipher - overhaul memory management") Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin

crypto: af_alg - limit RX SG extraction by receive buffer budget

2026-04-22T11:22:24+00:00

[ Upstream commit 8eceab19eba9dcbfd2a0daec72e1bf48aa100170 ] Make af_alg_get_rsgl() limit each RX scatterlist extraction to the remaining receive buffer budget. af_alg_get_rsgl() currently uses af_alg_readable() only as a gate before extracting data into the RX scatterlist. Limit each extraction to the remaining af_alg_rcvbuf(sk) budget so that receive-side accounting matches the amount of data attached to the request. If skcipher cannot obtain enough RX space for at least one chunk while more data remains to be processed, reject the recvmsg call instead of rounding the request length down to zero. Fixes: e870456d8e7c8d57c059ea479b5aadbb55ff4c3a ("crypto: algif_skcipher - overhaul memory management") Reported-by: Yifan Wu Reported-by: Juefei Pu Co-developed-by: Yuan Tan Signed-off-by: Yuan Tan Suggested-by: Xin Liu Signed-off-by: Douya Le Signed-off-by: Ren Wei Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin

crypto: algif_aead - Revert to operating out-of-place

2026-04-11T12:26:23+00:00

[ Upstream commit a664bf3d603dc3bdcf9ae47cc21e0daec706d7a5 ] This mostly reverts commit 72548b093ee3 except for the copying of the associated data. There is no benefit in operating in-place in algif_aead since the source and destination come from different mappings. Get rid of all the complexity added for in-place operation and just copy the AD directly. Fixes: 72548b093ee3 ("crypto: algif_aead - copy AAD from src to dst") Reported-by: Taeyang Lee <0wn@theori.io> Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin

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

2026-04-11T12:26:20+00:00

[ Upstream commit 62397b493e14107ae82d8b80938f293d95425bcb ] 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: 8ff590903d5f ("crypto: algif_skcipher - User-space interface for skcipher operations") Signed-off-by: Norbert Szetei Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin

crypto: af_alg - zero initialize memory allocated via sock_kmalloc

2026-01-02T11:57:27+00:00

commit 6f6e309328d53a10c0fe1f77dec2db73373179b6 upstream. Several crypto user API contexts and requests allocated with sock_kmalloc() were left uninitialized, relying on callers to set fields explicitly. This resulted in the use of uninitialized data in certain error paths or when new fields are added in the future. The ACVP patches also contain two user-space interface files: algif_kpp.c and algif_akcipher.c. These too rely on proper initialization of their context structures. A particular issue has been observed with the newly added 'inflight' variable introduced in af_alg_ctx by commit: 67b164a871af ("crypto: af_alg - Disallow multiple in-flight AIO requests") Because the context is not memset to zero after allocation, the inflight variable has contained garbage values. As a result, af_alg_alloc_areq() has incorrectly returned -EBUSY randomly when the garbage value was interpreted as true: https://github.com/gregkh/linux/blame/master/crypto/af_alg.c#L1209 The check directly tests ctx->inflight without explicitly comparing against true/false. Since inflight is only ever set to true or false later, an uninitialized value has triggered -EBUSY failures. Zero-initializing memory allocated with sock_kmalloc() ensures inflight and other fields start in a known state, removing random issues caused by uninitialized data. Fixes: fe869cdb89c9 ("crypto: algif_hash - User-space interface for hash operations") Fixes: 5afdfd22e6ba ("crypto: algif_rng - add random number generator support") Fixes: 2d97591ef43d ("crypto: af_alg - consolidation of duplicate code") Fixes: 67b164a871af ("crypto: af_alg - Disallow multiple in-flight AIO requests") Cc: stable@vger.kernel.org Signed-off-by: Shivani Agarwal Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman

crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg

2025-09-18T09:24:59+00:00

Issuing two writes to the same af_alg socket is bogus as the data will be interleaved in an unpredictable fashion. Furthermore, concurrent writes may create inconsistencies in the internal socket state. Disallow this by adding a new ctx->write field that indiciates exclusive ownership for writing. Fixes: 8ff590903d5 ("crypto: algif_skcipher - User-space interface for skcipher operations") Reported-by: Muhammad Alifa Ramdhan Reported-by: Bing-Jhong Billy Jheng Signed-off-by: Herbert Xu

crypto: af_alg - Set merge to zero early in af_alg_sendmsg

2025-09-18T09:24:38+00:00

If an error causes af_alg_sendmsg to abort, ctx->merge may contain a garbage value from the previous loop. This may then trigger a crash on the next entry into af_alg_sendmsg when it attempts to do a merge that can't be done. Fix this by setting ctx->merge to zero near the start of the loop. Fixes: 8ff590903d5 ("crypto: algif_skcipher - User-space interface for skcipher operations") Reported-by: Muhammad Alifa Ramdhan Reported-by: Bing-Jhong Billy Jheng Signed-off-by: Herbert Xu

crypto: Add missing MODULE_DESCRIPTION() macros

2024-05-31T09:34:56+00:00

Fix the 'make W=1' warnings: WARNING: modpost: missing MODULE_DESCRIPTION() in crypto/cast_common.o WARNING: modpost: missing MODULE_DESCRIPTION() in crypto/af_alg.o WARNING: modpost: missing MODULE_DESCRIPTION() in crypto/algif_hash.o WARNING: modpost: missing MODULE_DESCRIPTION() in crypto/algif_skcipher.o WARNING: modpost: missing MODULE_DESCRIPTION() in crypto/ecc.o WARNING: modpost: missing MODULE_DESCRIPTION() in crypto/curve25519-generic.o WARNING: modpost: missing MODULE_DESCRIPTION() in crypto/xor.o WARNING: modpost: missing MODULE_DESCRIPTION() in crypto/crypto_simd.o Signed-off-by: Jeff Johnson Signed-off-by: Herbert Xu