[syzbot] [crypto?] general protection fault in crypto_shash_final

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 37ff78e977f1 mlxsw: spectrum_nve_vxlan: Fix unsupported fl..
git tree: net-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=15132add280000
kernel config: https://syzkaller.appspot.com/x/.config?x=526f919910d4a671
dashboard link: https://syzkaller.appspot.com/bug?extid=14234ccf6d0ef629ec1a
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1009d065280000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16fdc72b280000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/41e829152d3c/disk-37ff78e9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a594b97acb02/vmlinux-37ff78e9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b41140b53372/bzImage-37ff78e9.xz

The issue was bisected to:

commit c662b043cdca89bf0f03fc37251000ac69a3a548
Author: David Howells <dhow...@redhat.com>
Date: Tue Jun 6 13:08:56 2023 +0000

crypto: af_alg/hash: Support MSG_SPLICE_PAGES

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1426f12d280000
final oops: https://syzkaller.appspot.com/x/report.txt?x=1626f12d280000
console output: https://syzkaller.appspot.com/x/log.txt?x=1226f12d280000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+14234c...@syzkaller.appspotmail.com
Fixes: c662b043cdca ("crypto: af_alg/hash: Support MSG_SPLICE_PAGES")

general protection fault, probably for non-canonical address 0xdffffc0000000004: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027]
CPU: 1 PID: 5006 Comm: kworker/1:3 Not tainted 6.4.0-rc5-syzkaller-00859-g37ff78e977f1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/25/2023
Workqueue: cryptd cryptd_queue_worker
RIP: 0010:crypto_shash_alg include/crypto/hash.h:827 [inline]
RIP: 0010:crypto_shash_final+0x49/0x120 crypto/shash.c:171
Code: fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 d5 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 5d 00 48 8d 7b 20 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 a8 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b
RSP: 0018:ffffc90003a3fca8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000004 RSI: ffffffff83df1715 RDI: 0000000000000020
RBP: ffff88801b756b08 R08: 0000000000000005 R09: 00000000ffffff8d
R10: 0000000000000000 R11: 1ffffffff21842f8 R12: ffff888029311988
R13: ffff88801b756b08 R14: ffff888014eaa600 R15: ffff8880b993bd80
FS: 0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6c11c57440 CR3: 00000000221e4000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
cryptd_hash_final+0xea/0x140 crypto/cryptd.c:580
crypto_request_complete include/crypto/algapi.h:272 [inline]
cryptd_queue_worker+0x130/0x1d0 crypto/cryptd.c:181
process_one_work+0x99a/0x15e0 kernel/workqueue.c:2405
worker_thread+0x67d/0x10c0 kernel/workqueue.c:2552
kthread+0x344/0x440 kernel/kthread.c:379
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:crypto_shash_alg include/crypto/hash.h:827 [inline]
RIP: 0010:crypto_shash_final+0x49/0x120 crypto/shash.c:171
Code: fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 d5 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 5d 00 48 8d 7b 20 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 a8 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b
RSP: 0018:ffffc90003a3fca8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000004 RSI: ffffffff83df1715 RDI: 0000000000000020
RBP: ffff88801b756b08 R08: 0000000000000005 R09: 00000000ffffff8d
R10: 0000000000000000 R11: 1ffffffff21842f8 R12: ffff888029311988
R13: ffff88801b756b08 R14: ffff888014eaa600 R15: ffff8880b993bd80
FS: 0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6c11c57440 CR3: 00000000221e4000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess), 3 bytes skipped:
0: 48 c1 ea 03 shr $0x3,%rdx
4: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
8: 0f 85 d5 00 00 00 jne 0xe3
e: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
15: fc ff df
18: 48 8b 5d 00 mov 0x0(%rbp),%rbx
1c: 48 8d 7b 20 lea 0x20(%rbx),%rdi
20: 48 89 fa mov %rdi,%rdx
23: 48 c1 ea 03 shr $0x3,%rdx
* 27: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
2b: 0f 85 a8 00 00 00 jne 0xd9
31: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
38: fc ff df
3b: 48 rex.W
3c: 8b .byte 0x8b


---
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If the bug is already fixed, let syzbot know by replying with:
#syz fix: exact-commit-title

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#syz test: git://repo/address.git branch-or-commit-hash
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#syz dup: exact-subject-of-another-report

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#syz undup

[David Howells]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git main

crypto: af_alg/hash: Fix recvmsg() after sendmsg(MSG_MORE)

If an AF_ALG socket bound to a hashing algorithm is sent a zero-length
message with MSG_MORE set and then recvmsg() is called without first
sending another message without MSG_MORE set to end the operation, an oops
will occur because the crypto context and result doesn't now get set up in
advance because hash_sendmsg() now defers that as long as possible in the
hope that it can use crypto_ahash_digest() - and then because the message
is zero-length, it the data wrangling loop is skipped.

Fix this by always making a pass of the loop, even in the case that no data
is provided to the sendmsg().

Fix also extract_iter_to_sg() to handle a zero-length iterator by returning
0 immediately.

Whilst we're at it, remove the code to create a kvmalloc'd scatterlist if
we get more than ALG_MAX_PAGES - this shouldn't happen.

Fixes: c662b043cdca ("crypto: af_alg/hash: Support MSG_SPLICE_PAGES")

Reported-by: syzbot+13a08c...@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/000000000000b9...@google.com/
Signed-off-by: David Howells <dhow...@redhat.com>
cc: Herbert Xu <her...@gondor.apana.org.au>
cc: "David S. Miller" <da...@davemloft.net>
cc: Eric Dumazet <edum...@google.com>
cc: Jakub Kicinski <ku...@kernel.org>
cc: Paolo Abeni <pab...@redhat.com>
cc: Jens Axboe <ax...@kernel.dk>
cc: Matthew Wilcox <wi...@infradead.org>
cc: linux-...@vger.kernel.org
cc: net...@vger.kernel.org

diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c
index dfb048cefb60..1176533a55c9 100644
--- a/crypto/algif_hash.c
+++ b/crypto/algif_hash.c
@@ -83,26 +83,14 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,

ctx->more = false;

- while (msg_data_left(msg)) {
+ do {
ctx->sgl.sgt.sgl = ctx->sgl.sgl;
ctx->sgl.sgt.nents = 0;
ctx->sgl.sgt.orig_nents = 0;

err = -EIO;
npages = iov_iter_npages(&msg->msg_iter, max_pages);
- if (npages == 0)
- goto unlock_free;
-
- if (npages > ARRAY_SIZE(ctx->sgl.sgl)) {
- err = -ENOMEM;
- ctx->sgl.sgt.sgl =
- kvmalloc(array_size(npages,
- sizeof(*ctx->sgl.sgt.sgl)),
- GFP_KERNEL);
- if (!ctx->sgl.sgt.sgl)
- goto unlock_free;
- }
- sg_init_table(ctx->sgl.sgl, npages);
+ sg_init_table(ctx->sgl.sgl, max_t(size_t, npages, 1));

ctx->sgl.need_unpin = iov_iter_extract_will_pin(&msg->msg_iter);

@@ -111,7 +99,8 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,
if (err < 0)
goto unlock_free;
len = err;
- sg_mark_end(ctx->sgl.sgt.sgl + ctx->sgl.sgt.nents - 1);
+ if (len > 0)
+ sg_mark_end(ctx->sgl.sgt.sgl + ctx->sgl.sgt.nents - 1);

if (!msg_data_left(msg)) {
err = hash_alloc_result(sk, ctx);
@@ -148,7 +137,7 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,

copied += len;
af_alg_free_sg(&ctx->sgl);
- }
+ } while (msg_data_left(msg));

ctx->more = msg->msg_flags & MSG_MORE;
err = 0;
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index e97d7060329e..77a7b18ee751 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -1340,7 +1340,7 @@ ssize_t extract_iter_to_sg(struct iov_iter *iter, size_t maxsize,
struct sg_table *sgtable, unsigned int sg_max,
iov_iter_extraction_t extraction_flags)
{
- if (maxsize == 0)
+ if (!maxsize || !iter->count)
return 0;

switch (iov_iter_type(iter)) {

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+14234c...@syzkaller.appspotmail.com

Tested on:

commit: fa0e21fa rtnetlink: extend RTEXT_FILTER_SKIP_STATS to ..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git main
console output: https://syzkaller.appspot.com/x/log.txt?x=13b86427280000

kernel config: https://syzkaller.appspot.com/x/.config?x=526f919910d4a671
dashboard link: https://syzkaller.appspot.com/bug?extid=14234ccf6d0ef629ec1a
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

patch: https://syzkaller.appspot.com/x/patch.diff?x=15bf213b280000

Note: testing is done by a robot and is best-effort only.