[syzbot] KASAN: use-after-free Read in __isofs_iget

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d3134eb5de85 Add linux-next specific files for 20211011
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13f5fd98b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=b9662326d2be383b
dashboard link: https://syzkaller.appspot.com/bug?extid=6fc7fb214625d82af7d1
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=15ca2e47300000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17869bd4b00000

Bisection is inconclusive: the issue happens on the oldest tested release.

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10808570b00000
final oops: https://syzkaller.appspot.com/x/report.txt?x=12808570b00000
console output: https://syzkaller.appspot.com/x/log.txt?x=14808570b00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6fc7fb...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 224
==================================================================
BUG: KASAN: use-after-free in isofs_read_inode fs/isofs/inode.c:1350 [inline]
BUG: KASAN: use-after-free in __isofs_iget fs/isofs/inode.c:1550 [inline]
BUG: KASAN: use-after-free in __isofs_iget+0x1c84/0x2100 fs/isofs/inode.c:1525
Read of size 1 at addr ffff88806ece6015 by task syz-executor936/6592

CPU: 0 PID: 6592 Comm: syz-executor936 Not tainted 5.15.0-rc4-next-20211011-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description.constprop.0.cold+0x8d/0x320 mm/kasan/report.c:247
__kasan_report mm/kasan/report.c:433 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:450
isofs_read_inode fs/isofs/inode.c:1350 [inline]
__isofs_iget fs/isofs/inode.c:1550 [inline]
__isofs_iget+0x1c84/0x2100 fs/isofs/inode.c:1525
isofs_iget fs/isofs/isofs.h:133 [inline]
isofs_export_iget fs/isofs/export.c:29 [inline]
isofs_export_iget fs/isofs/export.c:20 [inline]
isofs_fh_to_dentry fs/isofs/export.c:170 [inline]
isofs_fh_to_dentry+0x117/0x1f0 fs/isofs/export.c:162
exportfs_decode_fh_raw+0x127/0x7a0 fs/exportfs/expfs.c:436
exportfs_decode_fh+0x38/0x90 fs/exportfs/expfs.c:575
do_handle_to_path fs/fhandle.c:152 [inline]
handle_to_path fs/fhandle.c:207 [inline]
do_handle_open+0x2b6/0x8b0 fs/fhandle.c:223
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+0x44/0xae
RIP: 0033:0x7fa002798fb9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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:00007ffffcd5a438 EFLAGS: 00000246 ORIG_RAX: 0000000000000130
RAX: ffffffffffffffda RBX: 0000000000010939 RCX: 00007fa002798fb9
RDX: 0000000000000000 RSI: 0000000020000080 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000000 R09: 00007ffffcd5a460
R10: 00007ffffcd5a300 R11: 0000000000000246 R12: 00007ffffcd5a45c
R13: 00007ffffcd5a490 R14: 00007ffffcd5a470 R15: 000000000000000d
</TASK>

The buggy address belongs to the page:
page:ffffea0001bb3980 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x6ece6
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0001beb708 ffffea0001f38e48 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x400dc0(GFP_KERNEL_ACCOUNT|__GFP_ZERO), pid 6450, ts 55488123071, free_ts 55808040837
prep_new_page mm/page_alloc.c:2416 [inline]
get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4147
__alloc_pages+0x1b2/0x500 mm/page_alloc.c:5382
alloc_pages+0x1a7/0x300 mm/mempolicy.c:2191
__get_free_pages+0x8/0x40 mm/page_alloc.c:5431
_pgd_alloc arch/x86/mm/pgtable.c:414 [inline]
pgd_alloc+0x81/0x360 arch/x86/mm/pgtable.c:430
mm_alloc_pgd kernel/fork.c:639 [inline]
mm_init+0x60a/0xab0 kernel/fork.c:1125
mm_alloc+0x99/0xc0 kernel/fork.c:1153
bprm_mm_init fs/exec.c:368 [inline]
alloc_bprm+0x1c3/0x8f0 fs/exec.c:1523
do_execveat_common+0x232/0x780 fs/exec.c:1889
do_execve fs/exec.c:1990 [inline]
__do_sys_execve fs/exec.c:2066 [inline]
__se_sys_execve fs/exec.c:2061 [inline]
__x64_sys_execve+0x8f/0xc0 fs/exec.c:2061
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+0x44/0xae
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1336 [inline]
free_pcp_prepare+0x373/0x870 mm/page_alloc.c:1387
free_unref_page_prepare mm/page_alloc.c:3307 [inline]
free_unref_page+0x19/0x690 mm/page_alloc.c:3386
mm_free_pgd kernel/fork.c:647 [inline]
__mmdrop+0xcb/0x3f0 kernel/fork.c:749
mmdrop include/linux/sched/mm.h:49 [inline]
__mmput+0x3f1/0x4b0 kernel/fork.c:1174
mmput+0x56/0x60 kernel/fork.c:1185
exit_mm kernel/exit.c:507 [inline]
do_exit+0xb29/0x2b40 kernel/exit.c:819
do_group_exit+0x125/0x310 kernel/exit.c:929
__do_sys_exit_group kernel/exit.c:940 [inline]
__se_sys_exit_group kernel/exit.c:938 [inline]
__x64_sys_exit_group+0x3a/0x50 kernel/exit.c:938
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+0x44/0xae

Memory state around the buggy address:
ffff88806ece5f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88806ece5f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88806ece6000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88806ece6080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88806ece6100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
This report is generated by a bot. It may contain errors.
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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

[Jan Kara]

On Fri 15-10-21 17:35:19, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: d3134eb5de85 Add linux-next specific files for 20211011
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=13f5fd98b00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=b9662326d2be383b
> dashboard link: https://syzkaller.appspot.com/bug?extid=6fc7fb214625d82af7d1
> 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=15ca2e47300000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17869bd4b00000
>
> Bisection is inconclusive: the issue happens on the oldest tested release.
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10808570b00000
> final oops: https://syzkaller.appspot.com/x/report.txt?x=12808570b00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=14808570b00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+6fc7fb...@syzkaller.appspotmail.com

Let's try this:

#sys test 519d81956ee277b4419c723adfb154603c2565ba

Honza
--
Jan Kara <ja...@suse.com>
SUSE Labs, CR

[Jan Kara]

Bah, I've messed up the tag. So let's try again:

#syz test git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 519d81956ee277b4419c723adfb154603c2565ba

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+6fc7fb...@syzkaller.appspotmail.com

Tested on:

commit: 519d8195 Linux 5.15-rc6
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel config: https://syzkaller.appspot.com/x/.config?x=fd205ca848a57406

dashboard link: https://syzkaller.appspot.com/bug?extid=6fc7fb214625d82af7d1
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=101927c8b00000

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