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

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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    e431e712c836 Merge branch 'sfc-tc-encap-actions-offload'
git tree:       net-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=17e7771b280000
kernel config:  https://syzkaller.appspot.com/x/.config?x=526f919910d4a671
dashboard link: https://syzkaller.appspot.com/bug?extid=4e2e47f32607d0f72d43
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=12610c75280000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=171cdef1280000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/35e2db144233/disk-e431e712.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ecf37a1cef2c/vmlinux-e431e712.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a3da92090562/bzImage-e431e712.xz

The issue was bisected to:

commit c662b043cdca89bf0f03fc37251000ac69a3a548
Author: David Howells <dhowells@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=12392407280000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=11392407280000
console output: https://syzkaller.appspot.com/x/log.txt?x=16392407280000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4e2e47f32607d0f72d43@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: 0 PID: 9 Comm: kworker/0:1 Not tainted 6.4.0-rc5-syzkaller-01107-ge431e712c836 #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_finup+0x53/0x160 crypto/shash.c:198
Code: fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 05 01 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 d8 00 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b
RSP: 0018:ffffc900000e7ba0 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000004 RSI: ffffffff83df35bf RDI: 0000000000000020
RBP: ffff888028350b08 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 1ffffffff218470c R12: ffff8880123fa1c0
R13: ffff888029582ac8 R14: 0000000000000014 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f251034e440 CR3: 000000007cc84000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 shash_ahash_finup+0xdf/0x3a0 crypto/shash.c:333
 cryptd_hash_finup+0xce/0x120 crypto/cryptd.c:597
 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_finup+0x53/0x160 crypto/shash.c:198
Code: fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 05 01 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 d8 00 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b
RSP: 0018:ffffc900000e7ba0 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000004 RSI: ffffffff83df35bf RDI: 0000000000000020
RBP: ffff888028350b08 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 1ffffffff218470c R12: ffff8880123fa1c0
R13: ffff888029582ac8 R14: 0000000000000014 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f251034e440 CR3: 000000002aa8e000 CR4: 00000000003506f0
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 05 01 00 00    	jne    0x113
   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 d8 00 00 00    	jne    0x109
  31:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  38:	fc ff df
  3b:	4c                   	rex.WR
  3c:	8b                   	.byte 0x8b


---
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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
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Re: [syzbot] [crypto?] general protection fault in crypto_shash_finup

[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+13a08c0bf4d212766c3c@syzkaller.appspotmail.com
    Link: https://lore.kernel.org/r/000000000000b928f705fdeb873a@google.com/
    Signed-off-by: David Howells <dhowells@redhat.com>
    cc: Herbert Xu <herbert@gondor.apana.org.au>
    cc: "David S. Miller" <davem@davemloft.net>
    cc: Eric Dumazet <edumazet@google.com>
    cc: Jakub Kicinski <kuba@kernel.org>
    cc: Paolo Abeni <pabeni@redhat.com>
    cc: Jens Axboe <axboe@kernel.dk>
    cc: Matthew Wilcox <willy@infradead.org>
    cc: linux-crypto@vger.kernel.org
    cc: netdev@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)) {

Re: [syzbot] [crypto?] general protection fault in crypto_shash_finup

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+4e2e47f32607d0f72d43@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=129a0837280000
kernel config:  https://syzkaller.appspot.com/x/.config?x=526f919910d4a671
dashboard link: https://syzkaller.appspot.com/bug?extid=4e2e47f32607d0f72d43
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=14cfedfd280000

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