linux-kernel - Re: [Cluster-devel] [syzbot] UBSAN: shift-out-of-bounds in gfs2

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Date:   Thu, 13 Oct 2022 14:52:58 +0100
From:   Andrew Price <anprice@...hat.com>
To:     syzbot <syzbot+87a187973530ac822e3c@...kaller.appspotmail.com>
Cc:     agruenba@...hat.com, cluster-devel@...hat.com,
        linux-kernel@...r.kernel.org, rpeterso@...hat.com,
        syzkaller-bugs@...glegroups.com
Subject: Re: [Cluster-devel] [syzbot] UBSAN: shift-out-of-bounds in
 gfs2_getbuf

On 13/10/2022 14:31, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    493ffd6605b2 Merge tag 'ucount-rlimits-cleanups-for-v5.19'..

$ git describe --contains 493ffd6605b2
next-20221011~172

> git tree:       upstream

It would be useful to know the precise git tree.

> console output: https://syzkaller.appspot.com/x/log.txt?x=14620252880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d19f5d16783f901
> dashboard link: https://syzkaller.appspot.com/bug?extid=87a187973530ac822e3c
> compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/f1ff6481e26f/disk-493ffd66.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/101bd3c7ae47/vmlinux-493ffd66.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+87a187973530ac822e3c@...kaller.appspotmail.com
> 
> ================================================================================
> UBSAN: shift-out-of-bounds in fs/gfs2/meta_io.c:128:16

         shift = PAGE_SHIFT - sdp->sd_sb.sb_bsize_shift;
         index = blkno >> shift;             /* convert block to page */
         bufnum = blkno - (index << shift);  /* block buf index within 
page */

So likely fixed by commit 670f8ce56dd0632dc29a0322e188cc73ce3c6b92 
"gfs2: Check sb_bsize_shift after reading superblock" which has just 
been merged into mainline, but doesn't appear in next-20221011~172

Andy

> shift exponent 4294967293 is too large for 64-bit type 'u64' (aka 'unsigned long long')
> CPU: 0 PID: 10195 Comm: syz-executor.3 Not tainted 6.0.0-syzkaller-09423-g493ffd6605b2 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
> Call Trace:
>   <TASK>
>   __dump_stack lib/dump_stack.c:88 [inline]
>   dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106
>   ubsan_epilogue lib/ubsan.c:151 [inline]
>   __ubsan_handle_shift_out_of_bounds+0x33d/0x3b0 lib/ubsan.c:322
>   gfs2_getbuf+0x759/0x7d0 fs/gfs2/meta_io.c:128
>   gfs2_meta_read+0x153/0x910 fs/gfs2/meta_io.c:265
>   gfs2_meta_buffer+0x153/0x3a0 fs/gfs2/meta_io.c:491
>   gfs2_meta_inode_buffer fs/gfs2/meta_io.h:72 [inline]
>   gfs2_inode_refresh+0xab/0xe90 fs/gfs2/glops.c:472
>   gfs2_instantiate+0x15e/0x220 fs/gfs2/glock.c:515
>   gfs2_glock_holder_ready fs/gfs2/glock.c:1303 [inline]
>   gfs2_glock_wait+0x1d9/0x2a0 fs/gfs2/glock.c:1323
>   gfs2_glock_nq_init fs/gfs2/glock.h:263 [inline]
>   gfs2_lookupi+0x40c/0x650 fs/gfs2/inode.c:306
>   gfs2_lookup_simple+0xec/0x170 fs/gfs2/inode.c:258
>   init_journal+0x19b/0x22c0 fs/gfs2/ops_fstype.c:739
>   init_inodes+0xdc/0x340 fs/gfs2/ops_fstype.c:882
>   gfs2_fill_super+0x1ad8/0x2610 fs/gfs2/ops_fstype.c:1240
>   get_tree_bdev+0x400/0x620 fs/super.c:1323
>   gfs2_get_tree+0x50/0x210 fs/gfs2/ops_fstype.c:1323
>   vfs_get_tree+0x88/0x270 fs/super.c:1530
>   do_new_mount+0x289/0xad0 fs/namespace.c:3040
>   do_mount fs/namespace.c:3383 [inline]
>   __do_sys_mount fs/namespace.c:3591 [inline]
>   __se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3568
>   do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>   do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
>   entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7f0eed68cada
> Code: 48 c7 c2 b8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff eb d2 e8 b8 04 00 00 0f 1f 84 00 00 00 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f0eee73cf88 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
> RAX: ffffffffffffffda RBX: 0000000020000200 RCX: 00007f0eed68cada
> RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007f0eee73cfe0
> RBP: 00007f0eee73d020 R08: 00007f0eee73d020 R09: 0000000020000000
> R10: 0000000000000008 R11: 0000000000000202 R12: 0000000020000000
> R13: 0000000020000100 R14: 00007f0eee73cfe0 R15: 0000000020000080
>   </TASK>
> ================================================================================
> 
> 
> ---
> 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 syzkaller@...glegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>