[syzbot] KASAN: slab-out-of-bounds Write in ext4_write_inline_data_end

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 614cb2751d31 Merge tag 'trace-v5.14-rc6' of git://git.kern..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=130112c5300000
kernel config: https://syzkaller.appspot.com/x/.config?x=f61012d0b1cd846f
dashboard link: https://syzkaller.appspot.com/bug?extid=13146364637c7363a7de
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=104d7cc5300000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1333ce0e300000

The issue was bisected to:

commit a154d5d83d21af6b9ee32adc5dbcea5ac1fb534c
Author: Arnd Bergmann <ar...@arndb.de>
Date: Mon Mar 4 20:38:03 2019 +0000

net: ignore sysctl_devconf_inherit_init_net without SYSCTL

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13f970b6300000
final oops: https://syzkaller.appspot.com/x/report.txt?x=100570b6300000
console output: https://syzkaller.appspot.com/x/log.txt?x=17f970b6300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+131463...@syzkaller.appspotmail.com
Fixes: a154d5d83d21 ("net: ignore sysctl_devconf_inherit_init_net without SYSCTL")

==================================================================
BUG: KASAN: slab-out-of-bounds in ext4_write_inline_data fs/ext4/inline.c:245 [inline]
BUG: KASAN: slab-out-of-bounds in ext4_write_inline_data_end+0x4d4/0x960 fs/ext4/inline.c:754
Write of size 70 at addr ffff8880195444ef by task syz-executor279/8426

CPU: 0 PID: 8426 Comm: syz-executor279 Not tainted 5.14.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1ae/0x29f lib/dump_stack.c:105
print_address_description+0x66/0x3b0 mm/kasan/report.c:233
__kasan_report mm/kasan/report.c:419 [inline]
kasan_report+0x163/0x210 mm/kasan/report.c:436
check_region_inline mm/kasan/generic.c:135 [inline]
kasan_check_range+0x2b5/0x2f0 mm/kasan/generic.c:189
memcpy+0x3c/0x60 mm/kasan/shadow.c:66
ext4_write_inline_data fs/ext4/inline.c:245 [inline]
ext4_write_inline_data_end+0x4d4/0x960 fs/ext4/inline.c:754
ext4_write_end+0x1ff/0xbd0 fs/ext4/inode.c:1290
generic_perform_write+0x361/0x580 mm/filemap.c:3667
ext4_buffered_write_iter+0x41c/0x590 fs/ext4/file.c:269
ext4_file_write_iter+0x8f7/0x1b90 fs/ext4/file.c:519
call_write_iter include/linux/fs.h:2114 [inline]
new_sync_write fs/read_write.c:518 [inline]
vfs_write+0xa39/0xc90 fs/read_write.c:605
ksys_write+0x171/0x2a0 fs/read_write.c:658
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+0x44/0xae
RIP: 0033:0x44ac89
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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff12e8852f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000004ce4d0 RCX: 000000000044ac89
RDX: 0000000000000082 RSI: 0000000020000180 RDI: 0000000000000006
RBP: 000000000049de98 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 024645fc87234f45 R14: 26e1d8b70aefbc5b R15: 00000000004ce4d8

Allocated by task 1:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
__kasan_slab_alloc+0x96/0xd0 mm/kasan/common.c:467
kasan_slab_alloc include/linux/kasan.h:254 [inline]
slab_post_alloc_hook mm/slab.h:519 [inline]
slab_alloc_node mm/slub.c:2959 [inline]
slab_alloc mm/slub.c:2967 [inline]
kmem_cache_alloc+0x1d1/0x340 mm/slub.c:2972
kmem_cache_zalloc include/linux/slab.h:711 [inline]
acpi_os_acquire_object include/acpi/platform/aclinuxex.h:67 [inline]
acpi_ut_allocate_object_desc_dbg+0xd8/0x165 drivers/acpi/acpica/utobject.c:359
acpi_ut_create_internal_object_dbg+0x21/0x195 drivers/acpi/acpica/utobject.c:69
acpi_ds_build_internal_object+0x15f/0x732 drivers/acpi/acpica/dsobject.c:94
acpi_ds_create_node+0xe9/0x1a8 drivers/acpi/acpica/dsobject.c:281
acpi_ds_load2_end_op+0x7d0/0xebc drivers/acpi/acpica/dswload2.c:618
acpi_ds_exec_end_op+0x6ce/0x11d4 drivers/acpi/acpica/dswexec.c:637
acpi_ps_parse_loop+0xd9f/0x1cf0 drivers/acpi/acpica/psloop.c:525
acpi_ps_parse_aml+0x1d5/0x955 drivers/acpi/acpica/psparse.c:475
acpi_ps_execute_table+0x317/0x3ef drivers/acpi/acpica/psxface.c:295
acpi_ns_execute_table+0x436/0x5bf drivers/acpi/acpica/nsparse.c:116
acpi_ns_load_table+0x5e/0x120 drivers/acpi/acpica/nsload.c:71
acpi_tb_load_namespace+0x456/0x6b9 drivers/acpi/acpica/tbxfload.c:186
acpi_load_tables+0x45/0xf5 drivers/acpi/acpica/tbxfload.c:59
acpi_bus_init+0x9a/0x993 drivers/acpi/bus.c:1213
acpi_init+0x8c/0x22c drivers/acpi/bus.c:1324
do_one_initcall+0x197/0x3f0 init/main.c:1287
do_initcall_level+0x14a/0x1f5 init/main.c:1360
do_initcalls+0x4b/0x8c init/main.c:1376
kernel_init_freeable+0x3f1/0x57e init/main.c:1598
kernel_init+0x19/0x2a0 init/main.c:1490
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

The buggy address belongs to the object at ffff8880195444e0
which belongs to the cache Acpi-Operand of size 72
The buggy address is located 15 bytes inside of
72-byte region [ffff8880195444e0, ffff888019544528)
The buggy address belongs to the page:
page:ffffea0000655100 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888019544068 pfn:0x19544
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 ffffea0000654f88 ffffea0000654e08 ffff8880110c2b40
raw: ffff888019544068 000000000027001d 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 1, ts 3012488798, free_ts 0
prep_new_page mm/page_alloc.c:2436 [inline]
get_page_from_freelist+0x779/0xa30 mm/page_alloc.c:4169
__alloc_pages+0x26c/0x5f0 mm/page_alloc.c:5391
alloc_page_interleave+0x22/0x1c0 mm/mempolicy.c:2119
alloc_slab_page mm/slub.c:1691 [inline]
allocate_slab+0xf1/0x540 mm/slub.c:1831
new_slab mm/slub.c:1894 [inline]
new_slab_objects mm/slub.c:2640 [inline]
___slab_alloc+0x1cf/0x350 mm/slub.c:2803
__slab_alloc mm/slub.c:2843 [inline]
slab_alloc_node mm/slub.c:2925 [inline]
slab_alloc mm/slub.c:2967 [inline]
kmem_cache_alloc+0x299/0x340 mm/slub.c:2972
kmem_cache_zalloc include/linux/slab.h:711 [inline]
acpi_os_acquire_object include/acpi/platform/aclinuxex.h:67 [inline]
acpi_ut_allocate_object_desc_dbg+0xd8/0x165 drivers/acpi/acpica/utobject.c:359
acpi_ut_create_internal_object_dbg+0x21/0x195 drivers/acpi/acpica/utobject.c:69
acpi_ds_build_internal_object+0x15f/0x732 drivers/acpi/acpica/dsobject.c:94
acpi_ds_create_node+0xe9/0x1a8 drivers/acpi/acpica/dsobject.c:281
acpi_ds_load2_end_op+0x7d0/0xebc drivers/acpi/acpica/dswload2.c:618
acpi_ds_exec_end_op+0x6ce/0x11d4 drivers/acpi/acpica/dswexec.c:637
acpi_ps_parse_loop+0xd9f/0x1cf0 drivers/acpi/acpica/psloop.c:525
acpi_ps_parse_aml+0x1d5/0x955 drivers/acpi/acpica/psparse.c:475
acpi_ps_execute_table+0x317/0x3ef drivers/acpi/acpica/psxface.c:295
acpi_ns_execute_table+0x436/0x5bf drivers/acpi/acpica/nsparse.c:116
page_owner free stack trace missing

Memory state around the buggy address:
ffff888019544400: fc fc 00 00 00 00 00 00 00 00 00 fc fc fc fc 00
ffff888019544480: 00 00 00 00 00 00 00 00 fc fc fc fc 00 00 00 00
>ffff888019544500: 00 00 00 00 00 fc fc fc fc fb fb fb fb fb fb fb
^
ffff888019544580: fb fb fc fc fc fc 00 00 00 00 00 00 00 00 00 fc
ffff888019544600: fc fc fc 00 00 00 00 00 00 00 00 00 fc fc fc fc
==================================================================
----------------
Code disassembly (best guess), 1 bytes skipped:
0: ff c3 inc %ebx
2: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1)
9: 00 00 00
c: 0f 1f 40 00 nopl 0x0(%rax)
10: 48 89 f8 mov %rdi,%rax
13: 48 89 f7 mov %rsi,%rdi
16: 48 89 d6 mov %rdx,%rsi
19: 48 89 ca mov %rcx,%rdx
1c: 4d 89 c2 mov %r8,%r10
1f: 4d 89 c8 mov %r9,%r8
22: 4c 8b 4c 24 08 mov 0x8(%rsp),%r9
27: 0f 05 syscall
29: 48 3d 01 f0 ff ff cmp $0xfffffffffffff001,%rax <-- trapping instruction
2f: 73 01 jae 0x32
31: c3 retq
32: 48 c7 c1 b8 ff ff ff mov $0xffffffffffffffb8,%rcx
39: f7 d8 neg %eax
3b: 64 89 01 mov %eax,%fs:(%rcx)
3e: 48 rex.W


---
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 syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
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

[Theodore Ts'o]

On Thu, Aug 19, 2021 at 01:10:18AM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 614cb2751d31 Merge tag 'trace-v5.14-rc6' of git://git.kern..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=130112c5300000
> kernel config: https://syzkaller.appspot.com/x/.config?x=f61012d0b1cd846f
> dashboard link: https://syzkaller.appspot.com/bug?extid=13146364637c7363a7de
> compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=104d7cc5300000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1333ce0e300000
>
> The issue was bisected to:
>
> commit a154d5d83d21af6b9ee32adc5dbcea5ac1fb534c
> Author: Arnd Bergmann <ar...@arndb.de>
> Date: Mon Mar 4 20:38:03 2019 +0000
>
> net: ignore sysctl_devconf_inherit_init_net without SYSCTL
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13f970b6300000
> final oops: https://syzkaller.appspot.com/x/report.txt?x=100570b6300000
> console output: https://syzkaller.appspot.com/x/log.txt?x=17f970b6300000

In case it wasn't obvious, this is a bogus bisection. It's a bug
ext4's inline_data support where there is a race between writing to an
inline_data file against setting extended attributes on that same
inline_data file.

Fix is coming up....

- Ted

[Theodore Ts'o]

The location of the system.data extended attribute can change whenever
xattr_sem is not taken. So we need to recalculate the i_inline_off
field since it mgiht have changed between ext4_write_begin() and
ext4_write_end().

This means that caching i_inline_off is probably not helpful, so in
the long run we should probably get rid of it and shrink the in-memory
ext4 inode slightly, but let's fix the race the simple way for now.

Cc: sta...@kernel.org
Fixes: f19d5870cbf72 ("ext4: add normal write support for inline data")
Reported-by: syzbot+131463...@syzkaller.appspotmail.com
Signed-off-by: Theodore Ts'o <ty...@mit.edu>
---
fs/ext4/inline.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
index 70cb64db33f7..24e994e75f5c 100644
--- a/fs/ext4/inline.c
+++ b/fs/ext4/inline.c
@@ -750,6 +750,12 @@ int ext4_write_inline_data_end(struct inode *inode, loff_t pos, unsigned len,
ext4_write_lock_xattr(inode, &no_expand);
BUG_ON(!ext4_has_inline_data(inode));

+ /*
+ * ei->i_inline_off may have changed since ext4_write_begin()
+ * called ext4_try_to_write_inline_data()
+ */
+ (void) ext4_find_inline_data_nolock(inode);
+
kaddr = kmap_atomic(page);
ext4_write_inline_data(inode, &iloc, kaddr, pos, len);
kunmap_atomic(kaddr);
--
2.31.0

[Theodore Ts'o]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git 9e445093e523f3277081314c864f708fd4bd34aa

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+131463...@syzkaller.appspotmail.com

Tested on:

commit: 9e445093 ext4: fix race writing to an inline_data file..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git
kernel config: https://syzkaller.appspot.com/x/.config?x=300aea483211c875

dashboard link: https://syzkaller.appspot.com/bug?extid=13146364637c7363a7de
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1

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