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

[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=15a22943280000
kernel config: https://syzkaller.appspot.com/x/.config?x=526f919910d4a671
dashboard link: https://syzkaller.appspot.com/bug?extid=472626bb5e7c59fb768f
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=133e0463280000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1543e995280000

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=15c78453280000
final oops: https://syzkaller.appspot.com/x/report.txt?x=17c78453280000
console output: https://syzkaller.appspot.com/x/log.txt?x=13c78453280000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+472626...@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: 5002 Comm: syz-executor421 Not tainted 6.4.0-rc5-syzkaller-00859-g37ff78e977f1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/25/2023
RIP: 0010:crypto_shash_alg include/crypto/hash.h:827 [inline]
RIP: 0010:crypto_shash_export include/crypto/hash.h:956 [inline]
RIP: 0010:shash_async_export+0x47/0xa0 crypto/shash.c:389
Code: 00 fc ff df 4c 89 e2 48 c1 ea 03 80 3c 02 00 75 4e 48 b8 00 00 00 00 00 fc ff df 48 8b 5b 50 48 8d 7b 20 48 89 fa 48 c1 ea 03 <80> 3c 02 00 75 40 48 b8 00 00 00 00 00 fc ff df 48 8b 5b 20 48 8d
RSP: 0018:ffffc900038afd20 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000004 RSI: ffffffff83df0723 RDI: 0000000000000020
RBP: 0000000000000010 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 000000000000064d R12: ffff8880766612f8
R13: 0000000000000001 R14: ffff888077e0aa00 R15: ffff88802927ea48
FS: 00005555557db300(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f069bf4bfd8 CR3: 00000000773e6000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
crypto_ahash_export include/crypto/hash.h:523 [inline]
hash_accept+0x229/0x670 crypto/algif_hash.c:286
hash_accept_nokey+0x67/0x90 crypto/algif_hash.c:416
do_accept+0x380/0x510 net/socket.c:1883
__sys_accept4_file net/socket.c:1924 [inline]
__sys_accept4+0x9a/0x120 net/socket.c:1954
__do_sys_accept net/socket.c:1971 [inline]
__se_sys_accept net/socket.c:1968 [inline]
__x64_sys_accept+0x75/0xb0 net/socket.c:1968
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f069bf04c39
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc03b39588 EFLAGS: 00000246 ORIG_RAX: 000000000000002b
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f069bf04c39
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007f069bec8de0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f069bec8e70
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:crypto_shash_alg include/crypto/hash.h:827 [inline]
RIP: 0010:crypto_shash_export include/crypto/hash.h:956 [inline]
RIP: 0010:shash_async_export+0x47/0xa0 crypto/shash.c:389
Code: 00 fc ff df 4c 89 e2 48 c1 ea 03 80 3c 02 00 75 4e 48 b8 00 00 00 00 00 fc ff df 48 8b 5b 50 48 8d 7b 20 48 89 fa 48 c1 ea 03 <80> 3c 02 00 75 40 48 b8 00 00 00 00 00 fc ff df 48 8b 5b 20 48 8d
RSP: 0018:ffffc900038afd20 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000004 RSI: ffffffff83df0723 RDI: 0000000000000020
RBP: 0000000000000010 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 000000000000064d R12: ffff8880766612f8
R13: 0000000000000001 R14: ffff888077e0aa00 R15: ffff88802927ea48
FS: 00005555557db300(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000558cc7d83000 CR3: 00000000773e6000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess), 3 bytes skipped:
0: df 4c 89 e2 fisttps -0x1e(%rcx,%rcx,4)
4: 48 c1 ea 03 shr $0x3,%rdx
8: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
c: 75 4e jne 0x5c
e: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
15: fc ff df
18: 48 8b 5b 50 mov 0x50(%rbx),%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: 75 40 jne 0x6d
2d: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
34: fc ff df
37: 48 8b 5b 20 mov 0x20(%rbx),%rbx
3b: 48 rex.W
3c: 8d .byte 0x8d


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection

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

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to change bug's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the bug is a duplicate of another bug, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#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+472626...@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=149b6617280000

kernel config: https://syzkaller.appspot.com/x/.config?x=526f919910d4a671
dashboard link: https://syzkaller.appspot.com/bug?extid=472626bb5e7c59fb768f
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=154a41fd280000

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