[v6.6] WARNING in smb2_add_credits

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c5596480c50e Linux 6.6.145
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17585632580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0bc3d90c30838b5
dashboard link: https://syzkaller.appspot.com/bug?extid=04d6a0157da850d58691
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/eb5cda0a8020/disk-c5596480.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ca05ff2fc502/vmlinux-c5596480.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6daf3255b985/bzImage-c5596480.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+04d6a0...@syzkaller.appspotmail.com

CIFS: VFS: \\127.0.0.1 Error -32 sending data on socket to server
------------[ cut here ]------------
WARNING: CPU: 0 PID: 15513 at fs/smb/client/smb2ops.c:97 smb2_add_credits+0x1365/0x2600 fs/smb/client/smb2ops.c:97
Modules linked in:
CPU: 0 PID: 15513 Comm: syz.0.2372 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:smb2_add_credits+0x1365/0x2600 fs/smb/client/smb2ops.c:97
Code: 03 42 80 3c 28 00 74 08 4c 89 e7 e8 55 b4 3c ff 49 8b 34 24 48 c7 c7 20 20 f7 8a e8 75 15 de 07 e9 eb f9 ff ff e8 bb 36 e4 fe <0f> 0b e9 d9 ef ff ff e8 af 36 e4 fe c6 05 0d c3 d3 0b 01 48 c7 c7
RSP: 0018:ffffc9000393f400 EFLAGS: 00010283
RAX: ffffffff82a33e15 RBX: ffff88807cd262c0 RCX: 0000000000080000
RDX: ffffc9000f92a000 RSI: 000000000003f46d RDI: 000000000003f46e
RBP: 0000000000000200 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000727e70 R12: 1ffff1100f9a4c58
R13: dffffc0000000000 R14: ffff88807cd26000 R15: 0000000000000000
FS: 00007f350c8096c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9b6d224ff8 CR3: 0000000024fef000 CR4: 00000000003506f0
Call Trace:
<TASK>
add_credits fs/smb/client/cifsglob.h:884 [inline]
compound_send_recv+0x1254/0x3040 fs/smb/client/transport.c:1193
cifs_send_recv+0x40/0x50 fs/smb/client/transport.c:1317
SMB2_negotiate+0x16b5/0x4270 fs/smb/client/smb2pdu.c:1144
cifs_negotiate_protocol+0x27a/0x670 fs/smb/client/connect.c:4008
cifs_get_smb_ses+0x8d6/0x1b00 fs/smb/client/connect.c:2434
cifs_mount_get_session+0xef/0x440 fs/smb/client/connect.c:3472
get_session fs/smb/client/dfs.c:62 [inline]
dfs_mount_share+0x1e9/0x7b0 fs/smb/client/dfs.c:285
cifs_mount+0xbc/0x650 fs/smb/client/connect.c:3720
cifs_smb3_do_mount+0x2e5/0x710 fs/smb/client/cifsfs.c:950
smb3_get_tree_common fs/smb/client/fs_context.c:785 [inline]
smb3_get_tree+0x5a5/0xa90 fs/smb/client/fs_context.c:805
vfs_get_tree+0x8c/0x280 fs/super.c:1764
vfs_cmd_create+0xe3/0x230 fs/fsopen.c:236
__do_sys_fsconfig fs/fsopen.c:481 [inline]
__se_sys_fsconfig+0x70a/0x850 fs/fsopen.c:355
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f350b99de99
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f350c809028 EFLAGS: 00000246 ORIG_RAX: 00000000000001af
RAX: ffffffffffffffda RBX: 00007f350bc25fa0 RCX: 00007f350b99de99
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000004
RBP: 00007f350ba33eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f350bc26038 R14: 00007f350bc25fa0 R15: 00007ffc1c71ad08
</TASK>


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: a1153c0deb44 Linux 6.6.147
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=174f0649580000

kernel config: https://syzkaller.appspot.com/x/.config?x=f0bc3d90c30838b5
dashboard link: https://syzkaller.appspot.com/bug?extid=04d6a0157da850d58691
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1130ee32580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9f646bfa1b52/disk-a1153c0d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a2aec2e8f0fd/vmlinux-a1153c0d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a7abe1f87405/bzImage-a1153c0d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+04d6a0...@syzkaller.appspotmail.com

cifs_smb3_do_mount: 14 callbacks suppressed
CIFS: Attempting to mount //127.0.0.1/share
CIFS: VFS: \\127.0.0.1 Error -104 sending data on socket to server
------------[ cut here ]------------
WARNING: CPU: 0 PID: 6330 at fs/smb/client/smb2ops.c:97 smb2_add_credits+0x1365/0x2600 fs/smb/client/smb2ops.c:97
Modules linked in:
CPU: 0 PID: 6330 Comm: syz.1.102 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:smb2_add_credits+0x1365/0x2600 fs/smb/client/smb2ops.c:97

Code: 03 42 80 3c 28 00 74 08 4c 89 e7 e8 15 b4 3c ff 49 8b 34 24 48 c7 c7 20 20 f7 8a e8 15 0b de 07 e9 eb f9 ff ff e8 ab 36 e4 fe <0f> 0b e9 d9 ef ff ff e8 9f 36 e4 fe c6 05 ad c8 d3 0b 01 48 c7 c7
RSP: 0018:ffffc90004ecf400 EFLAGS: 00010293
RAX: ffffffff82a33875 RBX: ffff88805b5f42c0 RCX: ffff888023a48000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000

RBP: 0000000000000200 R08: 0000000000000003 R09: 0000000000000004

R10: dffffc0000000000 R11: fffff520009d9e70 R12: 1ffff1100b6be858
R13: dffffc0000000000 R14: ffff88805b5f4000 R15: 0000000000000000
FS: 00007ffaf25076c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00002000000000c0 CR3: 0000000079436000 CR4: 00000000003506f0

Call Trace:
<TASK>
add_credits fs/smb/client/cifsglob.h:884 [inline]
compound_send_recv+0x1254/0x3040 fs/smb/client/transport.c:1193
cifs_send_recv+0x40/0x50 fs/smb/client/transport.c:1317
SMB2_negotiate+0x16b5/0x4270 fs/smb/client/smb2pdu.c:1144

cifs_negotiate_protocol+0x445/0x670 fs/smb/client/connect.c:4008

cifs_get_smb_ses+0x8d6/0x1b00 fs/smb/client/connect.c:2434
cifs_mount_get_session+0xef/0x440 fs/smb/client/connect.c:3472
get_session fs/smb/client/dfs.c:62 [inline]
dfs_mount_share+0x1e9/0x7b0 fs/smb/client/dfs.c:285
cifs_mount+0xbc/0x650 fs/smb/client/connect.c:3720
cifs_smb3_do_mount+0x2e5/0x710 fs/smb/client/cifsfs.c:950
smb3_get_tree_common fs/smb/client/fs_context.c:785 [inline]
smb3_get_tree+0x5a5/0xa90 fs/smb/client/fs_context.c:805
vfs_get_tree+0x8c/0x280 fs/super.c:1764
vfs_cmd_create+0xe3/0x230 fs/fsopen.c:236
__do_sys_fsconfig fs/fsopen.c:481 [inline]
__se_sys_fsconfig+0x70a/0x850 fs/fsopen.c:355
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

RIP: 0033:0x7ffaf159e019

Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 e8 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007ffaf2507028 EFLAGS: 00000246 ORIG_RAX: 00000000000001af
RAX: ffffffffffffffda RBX: 00007ffaf1825fa0 RCX: 00007ffaf159e019

RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000004

RBP: 00007ffaf163500c R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007ffaf1826038 R14: 00007ffaf1825fa0 R15: 00007ffdfd24f2a8
</TASK>


---
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