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When traceSMB is enabled through 'echo 1 > /proc/fs/cifs/traceSMB', after a mount, the following oops is triggered: [ 27.137943] BUG: unable to handle kernel paging request at ffff8800f80c268b [ 27.143396] PGD 2c6b067 P4D 2c6b067 PUD 0 [ 27.145386] Oops: 0000 [#1] SMP PTI [ 27.146186] CPU: 2 PID: 2655 Comm: mount.cifs Not tainted 4.17.0+ #39 [ 27.147174] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014 [ 27.148969] RIP: 0010:hex_dump_to_buffer+0x413/0x4b0 [ 27.149738] Code: 48 8b 44 24 08 31 db 45 31 d2 48 89 6c 24 18 44 89 6c 24 24 48 c7 c1 78 b5 23 82 4c 89 64 24 10 44 89 d5 41 89 dc 4c 8d 58 02 <44> 0f b7 00 4d 89 dd eb 1f 83 c5 01 41 01 c4 41 39 ef 0f 84 48 fe [ 27.152396] RSP: 0018:ffffc9000058f8c0 EFLAGS: 00010246 [ 27.153129] RAX: ffff8800f80c268b RBX: 0000000000000000 RCX: ffffffff8223b578 [ 27.153867] RDX: 0000000000000000 RSI: ffffffff81a55496 RDI: 0000000000000008 [ 27.154612] RBP: 0000000000000000 R08: 0000000000000020 R09: 0000000000000083 [ 27.155355] R10: 0000000000000000 R11: ffff8800f80c268d R12: 0000000000000000 [ 27.156101] R13: 0000000000000002 R14: ffffc9000058f94d R15: 0000000000000008 [ 27.156838] FS: 00007f1693a6b740(0000) GS:ffff88007fd00000(0000) knlGS:0000000000000000 [ 27.158354] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 27.159093] CR2: ffff8800f80c268b CR3: 00000000798fa001 CR4: 0000000000360ee0 [ 27.159892] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 27.160661] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 27.161464] Call Trace: [ 27.162123] print_hex_dump+0xd3/0x160 [ 27.162814] journal-offline (2658) used greatest stack depth: 13144 bytes left [ 27.162824] ? __release_sock+0x60/0xd0 [ 27.165344] ? tcp_sendmsg+0x31/0x40 [ 27.166177] dump_smb+0x39/0x40 [ 27.166972] ? vsnprintf+0x236/0x490 [ 27.167807] __smb_send_rqst.constprop.12+0x103/0x430 [ 27.168554] ? apic_timer_interrupt+0xa/0x20 [ 27.169306] smb_send_rqst+0x48/0xc0 [ 27.169984] cifs_send_recv+0xda/0x420 [ 27.170639] SMB2_negotiate+0x23d/0xfa0 [ 27.171301] ? vsnprintf+0x236/0x490 [ 27.171961] ? smb2_negotiate+0x19/0x30 [ 27.172586] smb2_negotiate+0x19/0x30 [ 27.173257] cifs_negotiate_protocol+0x70/0xd0 [ 27.173935] ? kstrdup+0x43/0x60 [ 27.174551] cifs_get_smb_ses+0x295/0xbe0 [ 27.175260] ? lock_timer_base+0x67/0x80 [ 27.175936] ? __internal_add_timer+0x1a/0x50 [ 27.176575] ? add_timer+0x10f/0x230 [ 27.177267] cifs_mount+0x101/0x1190 [ 27.177940] ? cifs_smb3_do_mount+0x144/0x5c0 [ 27.178575] cifs_smb3_do_mount+0x144/0x5c0 [ 27.179270] mount_fs+0x35/0x150 [ 27.179930] vfs_kern_mount.part.28+0x54/0xf0 [ 27.180567] do_mount+0x5ad/0xc40 [ 27.181234] ? kmem_cache_alloc_trace+0xed/0x1a0 [ 27.181916] ksys_mount+0x80/0xd0 [ 27.182535] __x64_sys_mount+0x21/0x30 [ 27.183220] do_syscall_64+0x4e/0x100 [ 27.183882] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 27.184535] RIP: 0033:0x7f169339055a [ 27.185192] Code: 48 8b 0d 41 d9 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 0e d9 2b 00 f7 d8 64 89 01 48 [ 27.187268] RSP: 002b:00007fff7b44eb58 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5 [ 27.188515] RAX: ffffffffffffffda RBX: 00007f1693a7e70e RCX: 00007f169339055a [ 27.189244] RDX: 000055b9f97f64e5 RSI: 000055b9f97f652c RDI: 00007fff7b45074f [ 27.189974] RBP: 000055b9fb8c9260 R08: 000055b9fb8ca8f0 R09: 0000000000000000 [ 27.190721] R10: 0000000000000000 R11: 0000000000000202 R12: 000055b9fb8ca8f0 [ 27.191429] R13: 0000000000000000 R14: 00007f1693a7c000 R15: 00007f1693a7e91d [ 27.192167] Modules linked in: [ 27.192797] CR2: ffff8800f80c268b [ 27.193435] ---[ end trace 67404c618badf323 ]--- The problem was that dump_smb() had been called with an invalid pointer, that is, in __smb_send_rqst(), iov[1] doesn't exist (n_vec == 1). This patch fixes it by relying on the n_vec value to dump out the smb packets. Signed-off-by: Paulo Alcantara <palcantara@suse.de> Signed-off-by: Steve French <stfrench@microsoft.com> Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.