[syzbot] KASAN: slab-out-of-bounds Read in io_uring_show_fdinfo

[syzbot] KASAN: slab-out-of-bounds Read in io_uring_show_fdinfo

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    a6afa4199d3d Merge tag 'mailbox-v6.1' of git://git.linaro...
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=10cfc3fa880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e2021a61197ebe02
dashboard link: https://syzkaller.appspot.com/bug?extid=e5198737e8a2d23d958c
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=108b448a880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13a0403a880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b8f297fb220e/disk-a6afa419.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9b6bc23e32ef/vmlinux-a6afa419.xz

The issue was bisected to:

commit 3b8fdd1dc35e395d19efbc8391a809a5b954ecf4
Author: Jens Axboe <axboe@kernel.dk>
Date:   Sun Sep 11 12:40:37 2022 +0000

    io_uring/fdinfo: fix sqe dumping for IORING_SETUP_SQE128

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1434f1ec880000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=1634f1ec880000
console output: https://syzkaller.appspot.com/x/log.txt?x=1234f1ec880000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e5198737e8a2d23d958c@syzkaller.appspotmail.com
Fixes: 3b8fdd1dc35e ("io_uring/fdinfo: fix sqe dumping for IORING_SETUP_SQE128")

==================================================================
BUG: KASAN: use-after-free in __io_uring_show_fdinfo io_uring/fdinfo.c:98 [inline]
BUG: KASAN: use-after-free in io_uring_show_fdinfo+0x625/0x1947 io_uring/fdinfo.c:206
Read of size 8 at addr ffff88806fbfff20 by task syz-executor255/3603

CPU: 0 PID: 3603 Comm: syz-executor255 Not tainted 6.0.0-syzkaller-09039-ga6afa4199d3d #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+0xcd/0x134 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:317 [inline]
 print_report.cold+0x2ba/0x719 mm/kasan/report.c:433
 kasan_report+0xb1/0x1e0 mm/kasan/report.c:495
 __io_uring_show_fdinfo io_uring/fdinfo.c:98 [inline]
 io_uring_show_fdinfo+0x625/0x1947 io_uring/fdinfo.c:206
 seq_show+0x587/0x800 fs/proc/fd.c:68
 seq_read_iter+0x4f5/0x1280 fs/seq_file.c:230
 seq_read+0x16d/0x210 fs/seq_file.c:162
 vfs_read+0x257/0x930 fs/read_write.c:468
 ksys_pread64 fs/read_write.c:665 [inline]
 __do_sys_pread64 fs/read_write.c:675 [inline]
 __se_sys_pread64 fs/read_write.c:672 [inline]
 __x64_sys_pread64+0x1f7/0x250 fs/read_write.c:672
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f7eb32dc369
Code: 28 c3 e8 1a 17 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:00007ffdd7256678 EFLAGS: 00000246 ORIG_RAX: 0000000000000011
RAX: ffffffffffffffda RBX: 00007ffdd7256780 RCX: 00007f7eb32dc369
RDX: 0000000000000011 RSI: 0000000020002140 RDI: 0000000000000005
RBP: 00007ffdd72566a0 R08: 00007ffdd7256510 R09: 0000000033303633
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffdd7256780
R13: 00007ffdd72566a0 R14: 00007f7eb33180a1 R15: 0000000000000000
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0001beffc0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x6fbff
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x8(__GFP_MOVABLE), pid 1, tgid 1 (swapper/0), ts 9881193944, free_ts 10384739419
 split_map_pages+0x1ef/0x520 mm/compaction.c:99
 isolate_freepages_range+0x30f/0x350 mm/compaction.c:737
 alloc_contig_range+0x2f6/0x490 mm/page_alloc.c:9331
 __alloc_contig_pages mm/page_alloc.c:9354 [inline]
 alloc_contig_pages+0x35a/0x4c0 mm/page_alloc.c:9431
 debug_vm_pgtable_alloc_huge_page mm/debug_vm_pgtable.c:1098 [inline]
 init_args mm/debug_vm_pgtable.c:1221 [inline]
 debug_vm_pgtable+0x88f/0x29d6 mm/debug_vm_pgtable.c:1259
 do_one_initcall+0xfe/0x650 init/main.c:1296
 do_initcall_level init/main.c:1369 [inline]
 do_initcalls init/main.c:1385 [inline]
 do_basic_setup init/main.c:1404 [inline]
 kernel_init_freeable+0x6b1/0x73a init/main.c:1623
 kernel_init+0x1a/0x1d0 init/main.c:1512
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1449 [inline]
 free_pcp_prepare+0x5e4/0xd20 mm/page_alloc.c:1499
 free_unref_page_prepare mm/page_alloc.c:3380 [inline]
 free_unref_page+0x19/0x4d0 mm/page_alloc.c:3476
 free_contig_range+0xb1/0x180 mm/page_alloc.c:9453
 destroy_args+0xa8/0x646 mm/debug_vm_pgtable.c:1031
 debug_vm_pgtable+0x2945/0x29d6 mm/debug_vm_pgtable.c:1354
 do_one_initcall+0xfe/0x650 init/main.c:1296
 do_initcall_level init/main.c:1369 [inline]
 do_initcalls init/main.c:1385 [inline]
 do_basic_setup init/main.c:1404 [inline]
 kernel_init_freeable+0x6b1/0x73a init/main.c:1623
 kernel_init+0x1a/0x1d0 init/main.c:1512
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

Memory state around the buggy address:
 ffff88806fbffe00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806fbffe80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88806fbfff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                               ^
 ffff88806fbfff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88806fc00000: fa fb fb fb fb fb fb fc fc fc fc fa fb fb fb fb
==================================================================


---
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

Re: [syzbot] KASAN: slab-out-of-bounds Read in io_uring_show_fdinfo

[Pavel Begunkov]

On 10/10/22 08:15, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    a6afa4199d3d Merge tag 'mailbox-v6.1' of git://git.linaro...
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=10cfc3fa880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e2021a61197ebe02
> dashboard link: https://syzkaller.appspot.com/bug?extid=e5198737e8a2d23d958c
> 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=108b448a880000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13a0403a880000

#syz test: https://github.com/isilence/linux.git io_uring/fdinfo_fix

-- 
Pavel Begunkov

Re: [syzbot] KASAN: slab-out-of-bounds Read in io_uring_show_fdinfo

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+e5198737e8a2d23d958c@syzkaller.appspotmail.com

Tested on:

commit:         4f408867 io_uring: fix sq shifts in fdinfo
git tree:       https://github.com/isilence/linux.git io_uring/fdinfo_fix
console output: https://syzkaller.appspot.com/x/log.txt?x=1529d51a880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b87022a508b2913f
dashboard link: https://syzkaller.appspot.com/bug?extid=e5198737e8a2d23d958c
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.