[syzbot] [squashfs?] KASAN: slab-out-of-bounds Write in squashfs_readahead (2)

[syzbot] [squashfs?] KASAN: slab-out-of-bounds Write in squashfs_readahead (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    13d88ac54ddd Merge tag 'vfs-6.7.fsid' of git://git.kernel...
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=121965ef680000
kernel config:  https://syzkaller.appspot.com/x/.config?x=beb32a598fd79db9
dashboard link: https://syzkaller.appspot.com/bug?extid=604424eb051c2f696163
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12b40c7b680000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10f691ef680000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9e81dc4903c2/disk-13d88ac5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f40fd7326b3f/vmlinux-13d88ac5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2f399cd6ff7d/bzImage-13d88ac5.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/8e127c645a04/mount_0.gz

The issue was bisected to:

commit f268eedddf3595e85f8883dc50aed29654785696
Author: Phillip Lougher <phillip@squashfs.org.uk>
Date:   Sat Jun 11 03:21:32 2022 +0000

    squashfs: extend "page actor" to handle missing pages

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1252b717680000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=1152b717680000
console output: https://syzkaller.appspot.com/x/log.txt?x=1652b717680000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+604424eb051c2f696163@syzkaller.appspotmail.com
Fixes: f268eedddf35 ("squashfs: extend "page actor" to handle missing pages")

SQUASHFS error: Unable to read metadata cache entry [6fa]
SQUASHFS error: Unable to read metadata cache entry [6fa]
SQUASHFS error: Unable to read metadata cache entry [6fa]
==================================================================
BUG: KASAN: slab-out-of-bounds in __readahead_batch include/linux/pagemap.h:1364 [inline]
BUG: KASAN: slab-out-of-bounds in squashfs_readahead+0x9a6/0x20d0 fs/squashfs/file.c:569
Write of size 8 at addr ffff88801e393648 by task syz-executor100/5067

CPU: 1 PID: 5067 Comm: syz-executor100 Not tainted 6.6.0-syzkaller-15156-g13d88ac54ddd #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0x163/0x540 mm/kasan/report.c:475
 kasan_report+0x142/0x170 mm/kasan/report.c:588
 __readahead_batch include/linux/pagemap.h:1364 [inline]
 squashfs_readahead+0x9a6/0x20d0 fs/squashfs/file.c:569
 read_pages+0x183/0x830 mm/readahead.c:160
 page_cache_ra_unbounded+0x68e/0x7c0 mm/readahead.c:269
 page_cache_sync_readahead include/linux/pagemap.h:1266 [inline]
 filemap_get_pages+0x49c/0x2080 mm/filemap.c:2497
 filemap_read+0x42b/0x10b0 mm/filemap.c:2593
 __kernel_read+0x425/0x8b0 fs/read_write.c:428
 integrity_kernel_read+0xb0/0xf0 security/integrity/iint.c:221
 ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:485 [inline]
 ima_calc_file_shash security/integrity/ima/ima_crypto.c:516 [inline]
 ima_calc_file_hash+0xad1/0x1b30 security/integrity/ima/ima_crypto.c:573
 ima_collect_measurement+0x554/0xb30 security/integrity/ima/ima_api.c:290
 process_measurement+0x1373/0x21c0 security/integrity/ima/ima_main.c:359
 ima_file_check+0xf1/0x170 security/integrity/ima/ima_main.c:557
 do_open fs/namei.c:3624 [inline]
 path_openat+0x2893/0x3280 fs/namei.c:3779
 do_filp_open+0x234/0x490 fs/namei.c:3809
 do_sys_openat2+0x13e/0x1d0 fs/open.c:1440
 do_sys_open fs/open.c:1455 [inline]
 __do_sys_open fs/open.c:1463 [inline]
 __se_sys_open fs/open.c:1459 [inline]
 __x64_sys_open+0x225/0x270 fs/open.c:1459
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f0e73d6c5f9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 61 17 00 00 90 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:00007ffd516ff158 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0031656c69662f2e RCX: 00007f0e73d6c5f9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200000c0
RBP: 00007f0e73ddf610 R08: 0000000000000225 R09: 0000000000000000
R10: 00007ffd516ff020 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffd516ff328 R14: 0000000000000001 R15: 0000000000000001
 </TASK>

Allocated by task 5067:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4f/0x70 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:383
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc+0xb9/0x230 mm/slab_common.c:1020
 kmalloc_array include/linux/slab.h:637 [inline]
 squashfs_readahead+0x30c/0x20d0 fs/squashfs/file.c:552
 read_pages+0x183/0x830 mm/readahead.c:160
 page_cache_ra_unbounded+0x68e/0x7c0 mm/readahead.c:269
 page_cache_sync_readahead include/linux/pagemap.h:1266 [inline]
 filemap_get_pages+0x49c/0x2080 mm/filemap.c:2497
 filemap_read+0x42b/0x10b0 mm/filemap.c:2593
 __kernel_read+0x425/0x8b0 fs/read_write.c:428
 integrity_kernel_read+0xb0/0xf0 security/integrity/iint.c:221
 ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:485 [inline]
 ima_calc_file_shash security/integrity/ima/ima_crypto.c:516 [inline]
 ima_calc_file_hash+0xad1/0x1b30 security/integrity/ima/ima_crypto.c:573
 ima_collect_measurement+0x554/0xb30 security/integrity/ima/ima_api.c:290
 process_measurement+0x1373/0x21c0 security/integrity/ima/ima_main.c:359
 ima_file_check+0xf1/0x170 security/integrity/ima/ima_main.c:557
 do_open fs/namei.c:3624 [inline]
 path_openat+0x2893/0x3280 fs/namei.c:3779
 do_filp_open+0x234/0x490 fs/namei.c:3809
 do_sys_openat2+0x13e/0x1d0 fs/open.c:1440
 do_sys_open fs/open.c:1455 [inline]
 __do_sys_open fs/open.c:1463 [inline]
 __se_sys_open fs/open.c:1459 [inline]
 __x64_sys_open+0x225/0x270 fs/open.c:1459
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

The buggy address belongs to the object at ffff88801e393640
 which belongs to the cache kmalloc-8 of size 8
The buggy address is located 0 bytes to the right of
 allocated 8-byte region [ffff88801e393640, ffff88801e393648)

The buggy address belongs to the physical page:
page:ffffea000078e4c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88801e393230 pfn:0x1e393
anon flags: 0xfff00000000800(slab|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000800 ffff888012c41280 0000000000000000 dead000000000001
raw: ffff88801e393230 0000000080660063 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, tgid 1 (swapper/0), ts 10649202635, free_ts 9358727270
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1e6/0x210 mm/page_alloc.c:1537
 prep_new_page mm/page_alloc.c:1544 [inline]
 get_page_from_freelist+0x339a/0x3530 mm/page_alloc.c:3312
 __alloc_pages+0x255/0x670 mm/page_alloc.c:4568
 alloc_pages_mpol+0x3de/0x640 mm/mempolicy.c:2133
 alloc_slab_page+0x6a/0x160 mm/slub.c:1870
 allocate_slab mm/slub.c:2017 [inline]
 new_slab+0x84/0x2f0 mm/slub.c:2070
 ___slab_alloc+0xc85/0x1310 mm/slub.c:3223
 __slab_alloc mm/slub.c:3322 [inline]
 __slab_alloc_node mm/slub.c:3375 [inline]
 slab_alloc_node mm/slub.c:3468 [inline]
 __kmem_cache_alloc_node+0x21d/0x300 mm/slub.c:3517
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc_node_track_caller+0xa5/0x230 mm/slab_common.c:1027
 kstrdup+0x3a/0x70 mm/util.c:62
 __kernfs_new_node+0x9d/0x870 fs/kernfs/dir.c:611
 kernfs_new_node+0x99/0x170 fs/kernfs/dir.c:679
 kernfs_create_link+0xa5/0x1f0 fs/kernfs/symlink.c:39
 sysfs_do_create_link_sd+0x85/0x100 fs/sysfs/symlink.c:44
 device_create_sys_dev_entry+0x10f/0x170 drivers/base/core.c:3451
 device_add+0x8cf/0xd30 drivers/base/core.c:3595
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1137 [inline]
 free_unref_page_prepare+0x92a/0xa50 mm/page_alloc.c:2347
 free_unref_page+0x37/0x3f0 mm/page_alloc.c:2487
 vfree+0x186/0x2e0 mm/vmalloc.c:2842
 delayed_vfree_work+0x56/0x80 mm/vmalloc.c:2763
 process_one_work kernel/workqueue.c:2630 [inline]
 process_scheduled_works+0x90f/0x1400 kernel/workqueue.c:2703
 worker_thread+0xa5f/0xff0 kernel/workqueue.c:2784
 kthread+0x2d3/0x370 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

Memory state around the buggy address:
 ffff88801e393500: 00 fc fc fc fc fa fc fc fc fc 05 fc fc fc fc 05
 ffff88801e393580: fc fc fc fc 00 fc fc fc fc 05 fc fc fc fc fa fc
>ffff88801e393600: fc fc fc 00 fc fc fc fc 00 fc fc fc fc 00 fc fc
                                              ^
 ffff88801e393680: fc fc 00 fc fc fc fc 00 fc fc fc fc 00 fc fc fc
 ffff88801e393700: fc 00 fc fc fc fc fb fc fc fc fc 00 fc fc fc fc
==================================================================


---
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Re: [syzbot] [squashfs?] KASAN: slab-out-of-bounds Write in squashfs_readahead (2)

[Phillip Lougher]

On Sun, Nov 12, 2023 at 5:32 AM syzbot
<syzbot+604424eb051c2f696163@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    13d88ac54ddd Merge tag 'vfs-6.7.fsid' of git://git.kernel...
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=121965ef680000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=beb32a598fd79db9
> dashboard link: https://syzkaller.appspot.com/bug?extid=604424eb051c2f696163
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12b40c7b680000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10f691ef680000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/9e81dc4903c2/disk-13d88ac5.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/f40fd7326b3f/vmlinux-13d88ac5.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/2f399cd6ff7d/bzImage-13d88ac5.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/8e127c645a04/mount_0.gz
>
> The issue was bisected to:
>
> commit f268eedddf3595e85f8883dc50aed29654785696
> Author: Phillip Lougher <phillip@squashfs.org.uk>
> Date:   Sat Jun 11 03:21:32 2022 +0000
>
>     squashfs: extend "page actor" to handle missing pages

Fixed the issue, and will send a patch shortly.

Phillip

>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1252b717680000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=1152b717680000
> console output: https://syzkaller.appspot.com/x/log.txt?x=1652b717680000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+604424eb051c2f696163@syzkaller.appspotmail.com
> Fixes: f268eedddf35 ("squashfs: extend "page actor" to handle missing pages")
>
> SQUASHFS error: Unable to read metadata cache entry [6fa]
> SQUASHFS error: Unable to read metadata cache entry [6fa]
> SQUASHFS error: Unable to read metadata cache entry [6fa]
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in __readahead_batch include/linux/pagemap.h:1364 [inline]
> BUG: KASAN: slab-out-of-bounds in squashfs_readahead+0x9a6/0x20d0 fs/squashfs/file.c:569
> Write of size 8 at addr ffff88801e393648 by task syz-executor100/5067
>
> CPU: 1 PID: 5067 Comm: syz-executor100 Not tainted 6.6.0-syzkaller-15156-g13d88ac54ddd #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
>  print_address_description mm/kasan/report.c:364 [inline]
>  print_report+0x163/0x540 mm/kasan/report.c:475
>  kasan_report+0x142/0x170 mm/kasan/report.c:588
>  __readahead_batch include/linux/pagemap.h:1364 [inline]
>  squashfs_readahead+0x9a6/0x20d0 fs/squashfs/file.c:569
>  read_pages+0x183/0x830 mm/readahead.c:160
>  page_cache_ra_unbounded+0x68e/0x7c0 mm/readahead.c:269
>  page_cache_sync_readahead include/linux/pagemap.h:1266 [inline]
>  filemap_get_pages+0x49c/0x2080 mm/filemap.c:2497
>  filemap_read+0x42b/0x10b0 mm/filemap.c:2593
>  __kernel_read+0x425/0x8b0 fs/read_write.c:428
>  integrity_kernel_read+0xb0/0xf0 security/integrity/iint.c:221
>  ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:485 [inline]
>  ima_calc_file_shash security/integrity/ima/ima_crypto.c:516 [inline]
>  ima_calc_file_hash+0xad1/0x1b30 security/integrity/ima/ima_crypto.c:573
>  ima_collect_measurement+0x554/0xb30 security/integrity/ima/ima_api.c:290
>  process_measurement+0x1373/0x21c0 security/integrity/ima/ima_main.c:359
>  ima_file_check+0xf1/0x170 security/integrity/ima/ima_main.c:557
>  do_open fs/namei.c:3624 [inline]
>  path_openat+0x2893/0x3280 fs/namei.c:3779
>  do_filp_open+0x234/0x490 fs/namei.c:3809
>  do_sys_openat2+0x13e/0x1d0 fs/open.c:1440
>  do_sys_open fs/open.c:1455 [inline]
>  __do_sys_open fs/open.c:1463 [inline]
>  __se_sys_open fs/open.c:1459 [inline]
>  __x64_sys_open+0x225/0x270 fs/open.c:1459
>  do_syscall_x64 arch/x86/entry/common.c:51 [inline]
>  do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
>  entry_SYSCALL_64_after_hwframe+0x63/0x6b
> RIP: 0033:0x7f0e73d6c5f9
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 61 17 00 00 90 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:00007ffd516ff158 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
> RAX: ffffffffffffffda RBX: 0031656c69662f2e RCX: 00007f0e73d6c5f9
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200000c0
> RBP: 00007f0e73ddf610 R08: 0000000000000225 R09: 0000000000000000
> R10: 00007ffd516ff020 R11: 0000000000000246 R12: 0000000000000001
> R13: 00007ffd516ff328 R14: 0000000000000001 R15: 0000000000000001
>  </TASK>
>
> Allocated by task 5067:
>  kasan_save_stack mm/kasan/common.c:45 [inline]
>  kasan_set_track+0x4f/0x70 mm/kasan/common.c:52
>  ____kasan_kmalloc mm/kasan/common.c:374 [inline]
>  __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:383
>  kasan_kmalloc include/linux/kasan.h:198 [inline]
>  __do_kmalloc_node mm/slab_common.c:1007 [inline]
>  __kmalloc+0xb9/0x230 mm/slab_common.c:1020
>  kmalloc_array include/linux/slab.h:637 [inline]
>  squashfs_readahead+0x30c/0x20d0 fs/squashfs/file.c:552
>  read_pages+0x183/0x830 mm/readahead.c:160
>  page_cache_ra_unbounded+0x68e/0x7c0 mm/readahead.c:269
>  page_cache_sync_readahead include/linux/pagemap.h:1266 [inline]
>  filemap_get_pages+0x49c/0x2080 mm/filemap.c:2497
>  filemap_read+0x42b/0x10b0 mm/filemap.c:2593
>  __kernel_read+0x425/0x8b0 fs/read_write.c:428
>  integrity_kernel_read+0xb0/0xf0 security/integrity/iint.c:221
>  ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:485 [inline]
>  ima_calc_file_shash security/integrity/ima/ima_crypto.c:516 [inline]
>  ima_calc_file_hash+0xad1/0x1b30 security/integrity/ima/ima_crypto.c:573
>  ima_collect_measurement+0x554/0xb30 security/integrity/ima/ima_api.c:290
>  process_measurement+0x1373/0x21c0 security/integrity/ima/ima_main.c:359
>  ima_file_check+0xf1/0x170 security/integrity/ima/ima_main.c:557
>  do_open fs/namei.c:3624 [inline]
>  path_openat+0x2893/0x3280 fs/namei.c:3779
>  do_filp_open+0x234/0x490 fs/namei.c:3809
>  do_sys_openat2+0x13e/0x1d0 fs/open.c:1440
>  do_sys_open fs/open.c:1455 [inline]
>  __do_sys_open fs/open.c:1463 [inline]
>  __se_sys_open fs/open.c:1459 [inline]
>  __x64_sys_open+0x225/0x270 fs/open.c:1459
>  do_syscall_x64 arch/x86/entry/common.c:51 [inline]
>  do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
>  entry_SYSCALL_64_after_hwframe+0x63/0x6b
>
> The buggy address belongs to the object at ffff88801e393640
>  which belongs to the cache kmalloc-8 of size 8
> The buggy address is located 0 bytes to the right of
>  allocated 8-byte region [ffff88801e393640, ffff88801e393648)
>
> The buggy address belongs to the physical page:
> page:ffffea000078e4c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88801e393230 pfn:0x1e393
> anon flags: 0xfff00000000800(slab|node=0|zone=1|lastcpupid=0x7ff)
> page_type: 0xffffffff()
> raw: 00fff00000000800 ffff888012c41280 0000000000000000 dead000000000001
> raw: ffff88801e393230 0000000080660063 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, tgid 1 (swapper/0), ts 10649202635, free_ts 9358727270
>  set_page_owner include/linux/page_owner.h:31 [inline]
>  post_alloc_hook+0x1e6/0x210 mm/page_alloc.c:1537
>  prep_new_page mm/page_alloc.c:1544 [inline]
>  get_page_from_freelist+0x339a/0x3530 mm/page_alloc.c:3312
>  __alloc_pages+0x255/0x670 mm/page_alloc.c:4568
>  alloc_pages_mpol+0x3de/0x640 mm/mempolicy.c:2133
>  alloc_slab_page+0x6a/0x160 mm/slub.c:1870
>  allocate_slab mm/slub.c:2017 [inline]
>  new_slab+0x84/0x2f0 mm/slub.c:2070
>  ___slab_alloc+0xc85/0x1310 mm/slub.c:3223
>  __slab_alloc mm/slub.c:3322 [inline]
>  __slab_alloc_node mm/slub.c:3375 [inline]
>  slab_alloc_node mm/slub.c:3468 [inline]
>  __kmem_cache_alloc_node+0x21d/0x300 mm/slub.c:3517
>  __do_kmalloc_node mm/slab_common.c:1006 [inline]
>  __kmalloc_node_track_caller+0xa5/0x230 mm/slab_common.c:1027
>  kstrdup+0x3a/0x70 mm/util.c:62
>  __kernfs_new_node+0x9d/0x870 fs/kernfs/dir.c:611
>  kernfs_new_node+0x99/0x170 fs/kernfs/dir.c:679
>  kernfs_create_link+0xa5/0x1f0 fs/kernfs/symlink.c:39
>  sysfs_do_create_link_sd+0x85/0x100 fs/sysfs/symlink.c:44
>  device_create_sys_dev_entry+0x10f/0x170 drivers/base/core.c:3451
>  device_add+0x8cf/0xd30 drivers/base/core.c:3595
> page last free stack trace:
>  reset_page_owner include/linux/page_owner.h:24 [inline]
>  free_pages_prepare mm/page_alloc.c:1137 [inline]
>  free_unref_page_prepare+0x92a/0xa50 mm/page_alloc.c:2347
>  free_unref_page+0x37/0x3f0 mm/page_alloc.c:2487
>  vfree+0x186/0x2e0 mm/vmalloc.c:2842
>  delayed_vfree_work+0x56/0x80 mm/vmalloc.c:2763
>  process_one_work kernel/workqueue.c:2630 [inline]
>  process_scheduled_works+0x90f/0x1400 kernel/workqueue.c:2703
>  worker_thread+0xa5f/0xff0 kernel/workqueue.c:2784
>  kthread+0x2d3/0x370 kernel/kthread.c:388
>  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
>
> Memory state around the buggy address:
>  ffff88801e393500: 00 fc fc fc fc fa fc fc fc fc 05 fc fc fc fc 05
>  ffff88801e393580: fc fc fc fc 00 fc fc fc fc 05 fc fc fc fc fa fc
> >ffff88801e393600: fc fc fc 00 fc fc fc fc 00 fc fc fc fc 00 fc fc
>                                               ^
>  ffff88801e393680: fc fc 00 fc fc fc fc 00 fc fc fc fc 00 fc fc fc
>  ffff88801e393700: fc 00 fc fc fc fc fb fc fc fc fc 00 fc fc fc fc
> ==================================================================
>
>
> ---
> 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@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
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup
>

[PATCH] squashfs: fix oob in squashfs_readahead

[Edward Adam Davis]

[Syz log]
SQUASHFS error: Failed to read block 0x6fc: -5
SQUASHFS error: Unable to read metadata cache entry [6fa]
SQUASHFS error: Unable to read metadata cache entry [6fa]
SQUASHFS error: Unable to read metadata cache entry [6fa]
==================================================================
BUG: KASAN: slab-out-of-bounds in __readahead_batch include/linux/pagemap.h:1364 [inline]
BUG: KASAN: slab-out-of-bounds in squashfs_readahead+0x9a6/0x20d0 fs/squashfs/file.c:569
Write of size 8 at addr ffff88801e393648 by task syz-executor100/5067

CPU: 1 PID: 5067 Comm: syz-executor100 Not tainted 6.6.0-syzkaller-15156-g13d88ac54ddd #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0x163/0x540 mm/kasan/report.c:475
 kasan_report+0x142/0x170 mm/kasan/report.c:588
 __readahead_batch include/linux/pagemap.h:1364 [inline]
 squashfs_readahead+0x9a6/0x20d0 fs/squashfs/file.c:569
 read_pages+0x183/0x830 mm/readahead.c:160
 page_cache_ra_unbounded+0x68e/0x7c0 mm/readahead.c:269
 page_cache_sync_readahead include/linux/pagemap.h:1266 [inline]
 filemap_get_pages+0x49c/0x2080 mm/filemap.c:2497
 filemap_read+0x42b/0x10b0 mm/filemap.c:2593
 __kernel_read+0x425/0x8b0 fs/read_write.c:428
 integrity_kernel_read+0xb0/0xf0 security/integrity/iint.c:221
 ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:485 [inline]
 ima_calc_file_shash security/integrity/ima/ima_crypto.c:516 [inline]
 ima_calc_file_hash+0xad1/0x1b30 security/integrity/ima/ima_crypto.c:573
 ima_collect_measurement+0x554/0xb30 security/integrity/ima/ima_api.c:290
 process_measurement+0x1373/0x21c0 security/integrity/ima/ima_main.c:359
 ima_file_check+0xf1/0x170 security/integrity/ima/ima_main.c:557
 do_open fs/namei.c:3624 [inline]
 path_openat+0x2893/0x3280 fs/namei.c:3779

[Bug]
path_openat() called open_last_lookups() before calling do_open() and 
open_last_lookups() will eventually call squashfs_read_inode() to set 
inode->i_size, but before setting i_size, it is necessary to obtain file_size 
from the disk.

However, during the value retrieval process, the length of the value retrieved
from the disk was greater than output->length, resulting(-EIO) in the failure of 
squashfs_read_data(), further leading to i_size has not been initialized, 
i.e. its value is 0.

This resulted in the failure of squashfs_read_data(), where "SQUASHFS error: 
Failed to read block 0x6fc: -5" was output in the syz log.
This also resulted in the failure of squashfs_cache_get(), outputting "SQUASHFS
error: Unable to read metadata cache entry [6fa]" in the syz log.

[Fix]
Before performing a read ahead operation in squashfs_read_folio() and 
squashfs_readahead(), check if i_size is not 0 before continuing.

Optimize the return value of squashfs_read_data() and return -EFBIG when the 
length is greater than output->length(or (index + length) >
msblk->bytes_used).

Reported-and-tested-by: syzbot+604424eb051c2f696163@syzkaller.appspotmail.com
Fixes: f268eedddf35 ("squashfs: extend "page actor" to handle missing pages")
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
---
 fs/squashfs/block.c | 2 +-
 fs/squashfs/file.c  | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c
index 581ce9519339..d335f28c822c 100644
--- a/fs/squashfs/block.c
+++ b/fs/squashfs/block.c
@@ -323,7 +323,7 @@ int squashfs_read_data(struct super_block *sb, u64 index, int length,
 	}
 	if (length < 0 || length > output->length ||
 			(index + length) > msblk->bytes_used) {
-		res = -EIO;
+		res = length < 0 ? -EIO : -EFBIG;
 		goto out;
 	}
 
diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c
index 8ba8c4c50770..5472ddd3596c 100644
--- a/fs/squashfs/file.c
+++ b/fs/squashfs/file.c
@@ -461,6 +461,11 @@ static int squashfs_read_folio(struct file *file, struct folio *folio)
 	TRACE("Entered squashfs_readpage, page index %lx, start block %llx\n",
 				page->index, squashfs_i(inode)->start);
 
+	if (!file_end) {
+		res = -EINVAL;
+		goto out;
+	}
+
 	if (page->index >= ((i_size_read(inode) + PAGE_SIZE - 1) >>
 					PAGE_SHIFT))
 		goto out;
@@ -547,6 +552,9 @@ static void squashfs_readahead(struct readahead_control *ractl)
 	int i, file_end = i_size_read(inode) >> msblk->block_log;
 	unsigned int max_pages = 1UL << shift;
 
+	if (!file_end)
+		return;
+
 	readahead_expand(ractl, start, (len | mask) + 1);
 
 	pages = kmalloc_array(max_pages, sizeof(void *), GFP_KERNEL);
-- 
2.25.1

Re: [PATCH] squashfs: fix oob in squashfs_readahead

[Andrew Morton]

On Wed, 15 Nov 2023 12:05:35 +0800 Edward Adam Davis <eadavis@qq.com> wrote:

> Before performing a read ahead operation in squashfs_read_folio() and 
> squashfs_readahead(), check if i_size is not 0 before continuing.

I'll merge this for testing, pending Phillip's review.  One thing:

> --- a/fs/squashfs/block.c
> +++ b/fs/squashfs/block.c
> @@ -323,7 +323,7 @@ int squashfs_read_data(struct super_block *sb, u64 index, int length,
>  	}
>  	if (length < 0 || length > output->length ||
>  			(index + length) > msblk->bytes_used) {
> -		res = -EIO;
> +		res = length < 0 ? -EIO : -EFBIG;
>  		goto out;
>  	}

Seems a bit ugly to test `length' twice for the same thing.  How about

	if (length < 0) {
		res = -EIO;
		got out;
	}
	if (length > output->length || (index + length) > msblk->bytes_used) {
		res = -EFBIG;
		goto out;
	}

?

Re: [PATCH] squashfs: fix oob in squashfs_readahead

[Phillip Lougher]

> [Bug]
> path_openat() called open_last_lookups() before calling do_open() and 
> open_last_lookups() will eventually call squashfs_read_inode() to set 
> inode->i_size, but before setting i_size, it is necessary to obtain file_size 
> from the disk.
> 
> However, during the value retrieval process, the length of the value retrieved
> from the disk was greater than output->length, resulting(-EIO) in the failure of 
> squashfs_read_data(), further leading to i_size has not been initialized, 
> i.e. its value is 0.
> 

NACK

This analysis is completely *wrong*.  First, if there was I/O error reading
the inode it would never be created, and squasfs_readahead() would
never be called on it, because it will never exist.

Second i_size isn't unintialised and it isn't 0 in value.  Where
you got this bogus information from is because in your test patches,
i.e.

https://lore.kernel.org/all/000000000000bb74b9060a14717c@google.com/

You have

+	if (!file_end) {
+		printk("i:%p, is:%d, %s\n", inode, i_size_read(inode), __func__);
+		res = -EINVAL;
+		goto out;
+	}
+

You have used %d, and the result of i_size_read(inode) overflows, giving the
bogus 0 value.

The actual value is 1407374883553280, or 0x5000000000000, which is
too big to fit into an unsigned int.

> This resulted in the failure of squashfs_read_data(), where "SQUASHFS error: 
> Failed to read block 0x6fc: -5" was output in the syz log.
> This also resulted in the failure of squashfs_cache_get(), outputting "SQUASHFS
> error: Unable to read metadata cache entry [6fa]" in the syz log.
> 

NO, *that* is caused by the failure to read some other inodes which
as a result are correctly not created.  Nothing to do with the oops here.

> [Fix]
> Before performing a read ahead operation in squashfs_read_folio() and 
> squashfs_readahead(), check if i_size is not 0 before continuing.
> 

A third NO, it is only 0 because the variable overflowed.

Additionally, let's look at your "fix" here.

> @@ -461,6 +461,11 @@ static int squashfs_read_folio(struct file *file, struct folio *folio)
>  	TRACE("Entered squashfs_readpage, page index %lx, start block %llx\n",
>  				page->index, squashfs_i(inode)->start);
>  
> +	if (!file_end) {
> +		res = -EINVAL;
> +		goto out;
> +	}
> +

file_end is computed by

	int file_end = i_size_read(inode) >> msblk->block_log;

So your "fix" will reject *any* file less than msblk->block_log in
size as invalid, including perfectly valid zero size files (empty
files are valid too).

I already identified the cause and send a fix patch here:

https://lore.kernel.org/all/20231113160901.6444-1-phillip@squashfs.org.uk/

NACK

Phillip

Re: [PATCH] squashfs: fix oob in squashfs_readahead

[Marek Szyprowski]

Hi All,

On 15.11.2023 05:05, Edward Adam Davis wrote:
> [Syz log]
> SQUASHFS error: Failed to read block 0x6fc: -5
> SQUASHFS error: Unable to read metadata cache entry [6fa]
> SQUASHFS error: Unable to read metadata cache entry [6fa]
> SQUASHFS error: Unable to read metadata cache entry [6fa]
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in __readahead_batch include/linux/pagemap.h:1364 [inline]
> BUG: KASAN: slab-out-of-bounds in squashfs_readahead+0x9a6/0x20d0 fs/squashfs/file.c:569
> Write of size 8 at addr ffff88801e393648 by task syz-executor100/5067
>
> CPU: 1 PID: 5067 Comm: syz-executor100 Not tainted 6.6.0-syzkaller-15156-g13d88ac54ddd #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
> Call Trace:
>   <TASK>
>   __dump_stack lib/dump_stack.c:88 [inline]
>   dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
>   print_address_description mm/kasan/report.c:364 [inline]
>   print_report+0x163/0x540 mm/kasan/report.c:475
>   kasan_report+0x142/0x170 mm/kasan/report.c:588
>   __readahead_batch include/linux/pagemap.h:1364 [inline]
>   squashfs_readahead+0x9a6/0x20d0 fs/squashfs/file.c:569
>   read_pages+0x183/0x830 mm/readahead.c:160
>   page_cache_ra_unbounded+0x68e/0x7c0 mm/readahead.c:269
>   page_cache_sync_readahead include/linux/pagemap.h:1266 [inline]
>   filemap_get_pages+0x49c/0x2080 mm/filemap.c:2497
>   filemap_read+0x42b/0x10b0 mm/filemap.c:2593
>   __kernel_read+0x425/0x8b0 fs/read_write.c:428
>   integrity_kernel_read+0xb0/0xf0 security/integrity/iint.c:221
>   ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:485 [inline]
>   ima_calc_file_shash security/integrity/ima/ima_crypto.c:516 [inline]
>   ima_calc_file_hash+0xad1/0x1b30 security/integrity/ima/ima_crypto.c:573
>   ima_collect_measurement+0x554/0xb30 security/integrity/ima/ima_api.c:290
>   process_measurement+0x1373/0x21c0 security/integrity/ima/ima_main.c:359
>   ima_file_check+0xf1/0x170 security/integrity/ima/ima_main.c:557
>   do_open fs/namei.c:3624 [inline]
>   path_openat+0x2893/0x3280 fs/namei.c:3779
>
> [Bug]
> path_openat() called open_last_lookups() before calling do_open() and
> open_last_lookups() will eventually call squashfs_read_inode() to set
> inode->i_size, but before setting i_size, it is necessary to obtain file_size
> from the disk.
>
> However, during the value retrieval process, the length of the value retrieved
> from the disk was greater than output->length, resulting(-EIO) in the failure of
> squashfs_read_data(), further leading to i_size has not been initialized,
> i.e. its value is 0.
>
> This resulted in the failure of squashfs_read_data(), where "SQUASHFS error:
> Failed to read block 0x6fc: -5" was output in the syz log.
> This also resulted in the failure of squashfs_cache_get(), outputting "SQUASHFS
> error: Unable to read metadata cache entry [6fa]" in the syz log.
>
> [Fix]
> Before performing a read ahead operation in squashfs_read_folio() and
> squashfs_readahead(), check if i_size is not 0 before continuing.
>
> Optimize the return value of squashfs_read_data() and return -EFBIG when the
> length is greater than output->length(or (index + length) >
> msblk->bytes_used).
>
> Reported-and-tested-by: syzbot+604424eb051c2f696163@syzkaller.appspotmail.com
> Fixes: f268eedddf35 ("squashfs: extend "page actor" to handle missing pages")
> Signed-off-by: Edward Adam Davis <eadavis@qq.com>

This patch, merged to linux-next as commit 1ff947abe24a ("squashfs: fix 
oob in squashfs_readahead"), breaks mounting squashfs volumes on all my 
test systems. Let me know if you need more information to debug this issue.

> ---
>   fs/squashfs/block.c | 2 +-
>   fs/squashfs/file.c  | 8 ++++++++
>   2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c
> index 581ce9519339..d335f28c822c 100644
> --- a/fs/squashfs/block.c
> +++ b/fs/squashfs/block.c
> @@ -323,7 +323,7 @@ int squashfs_read_data(struct super_block *sb, u64 index, int length,
>   	}
>   	if (length < 0 || length > output->length ||
>   			(index + length) > msblk->bytes_used) {
> -		res = -EIO;
> +		res = length < 0 ? -EIO : -EFBIG;
>   		goto out;
>   	}
>   
> diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c
> index 8ba8c4c50770..5472ddd3596c 100644
> --- a/fs/squashfs/file.c
> +++ b/fs/squashfs/file.c
> @@ -461,6 +461,11 @@ static int squashfs_read_folio(struct file *file, struct folio *folio)
>   	TRACE("Entered squashfs_readpage, page index %lx, start block %llx\n",
>   				page->index, squashfs_i(inode)->start);
>   
> +	if (!file_end) {
> +		res = -EINVAL;
> +		goto out;
> +	}
> +
>   	if (page->index >= ((i_size_read(inode) + PAGE_SIZE - 1) >>
>   					PAGE_SHIFT))
>   		goto out;
> @@ -547,6 +552,9 @@ static void squashfs_readahead(struct readahead_control *ractl)
>   	int i, file_end = i_size_read(inode) >> msblk->block_log;
>   	unsigned int max_pages = 1UL << shift;
>   
> +	if (!file_end)
> +		return;
> +
>   	readahead_expand(ractl, start, (len | mask) + 1);
>   
>   	pages = kmalloc_array(max_pages, sizeof(void *), GFP_KERNEL);

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: [PATCH] squashfs: fix oob in squashfs_readahead

[Andrew Morton]

On Fri, 17 Nov 2023 14:17:17 +0100 Marek Szyprowski <m.szyprowski@samsung.com> wrote:

> > Reported-and-tested-by: syzbot+604424eb051c2f696163@syzkaller.appspotmail.com
> > Fixes: f268eedddf35 ("squashfs: extend "page actor" to handle missing pages")
> > Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> 
> This patch, merged to linux-next as commit 1ff947abe24a ("squashfs: fix 
> oob in squashfs_readahead"), breaks mounting squashfs volumes on all my 
> test systems. Let me know if you need more information to debug this issue.

Thanks.  The patch has been dropped.

Re: [PATCH] squashfs: fix oob in squashfs_readahead

[Edward Adam Davis]

On Thu, 16 Nov 2023 15:14:24 +0000, Phillip Lougher wrote:
> > [Bug]
> > path_openat() called open_last_lookups() before calling do_open() and
> > open_last_lookups() will eventually call squashfs_read_inode() to set
> > inode->i_size, but before setting i_size, it is necessary to obtain file_size
> > from the disk.
> >
> > However, during the value retrieval process, the length of the value retrieved
> > from the disk was greater than output->length, resulting(-EIO) in the failure of
> > squashfs_read_data(), further leading to i_size has not been initialized,
> > i.e. its value is 0.
> >
> 
> NACK
> 
> This analysis is completely *wrong*.  First, if there was I/O error reading
> the inode it would never be created, and squasfs_readahead() would
> never be called on it, because it will never exist.
> 
> Second i_size isn't unintialised and it isn't 0 in value.  Where
> you got this bogus information from is because in your test patches,
> i.e.
[There is my debuging patch]
diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c
index 581ce9519339..1c7c5500206b 100644
--- a/fs/squashfs/block.c
+++ b/fs/squashfs/block.c
@@ -314,9 +314,11 @@ int squashfs_read_data(struct super_block *sb, u64 index, int length,
 		bio_uninit(bio);
 		kfree(bio);

+		printk("datal: %d \n", length);
 		compressed = SQUASHFS_COMPRESSED(length);
 		length = SQUASHFS_COMPRESSED_SIZE(length);
 		index += 2;
+		printk("datal2: %d, c:%d, i:%d \n", length, compressed, index);

 		TRACE("Block @ 0x%llx, %scompressed size %d\n", index - 2,
 		      compressed ? "" : "un", length);
@@ -324,6 +326,7 @@ int squashfs_read_data(struct super_block *sb, u64 index, int length,
 	if (length < 0 || length > output->length ||
 			(index + length) > msblk->bytes_used) {
 		res = -EIO;
+		printk("srd: l:%d, ol: %d, bu: %d \n", length, output->length, msblk->bytes_used);
 		goto out;
 	}

patch link: https://syzkaller.appspot.com/text?tag=Patch&x=1142f82f680000

[There is my test log]
[  457.030754][ T8879] datal: 65473
[  457.034334][ T8879] datal2: 32705, c:0, i:1788
[  457.039253][ T8879] srd: l:32705, ol: 8192, bu: 1870
[  457.044513][ T8879] SQUASHFS error: Failed to read block 0x6fc: -5
[  457.052034][ T8879] SQUASHFS error: Unable to read metadata cache entry [6fa]
log link: https://syzkaller.appspot.com/x/log.txt?x=137b0270e80000

[Answer your doubts]
Based on the above test, it can be clearly determined that length=32705 is 
greater than the maximum metadata size of 8192, resulting in squashfs_read_data() failed.
This will further lead to squashfs_cache_get() returns "entry->error=entry->length=-EIO", 
followed by squashfs_read_metadata() failed, which will ultimately result in i_size not 
being initialized in squashfs_read_inode().

The following are the relevant call stacks:
  23 const struct inode_operations squashfs_dir_inode_ops = {
  24         .lookup = squashfs_lookup,
  25         .listxattr = squashfs_listxattr
  26 };
  NORMAL  +0 ~0 -0  fs/squashfs/namei.c

  path_openat()->open_last_lookups()->lookup_open()
    1         if (d_in_lookup(dentry)) {
 3455                 struct dentry *res = dir_inode->i_op->lookup(dir_inode, dentry,                                                                                                                    1                                                              nd->flags);

 squashfs_lookup()->
	 squashfs_iget()->
	 squashfs_read_inode()-> 
	 init inode->i_size, example: inode->i_size = sqsh_ino->file_size;
> 
> https://lore.kernel.org/all/000000000000bb74b9060a14717c@google.com/
> 
> You have
> 
> +	if (!file_end) {
> +		printk("i:%p, is:%d, %s\n", inode, i_size_read(inode), __func__);
> +		res = -EINVAL;
> +		goto out;
> +	}
> +
> 
> You have used %d, and the result of i_size_read(inode) overflows, giving the
> bogus 0 value.
> 
> The actual value is 1407374883553280, or 0x5000000000000, which is
> too big to fit into an unsigned int.
> 
> > This resulted in the failure of squashfs_read_data(), where "SQUASHFS error:
> > Failed to read block 0x6fc: -5" was output in the syz log.
> > This also resulted in the failure of squashfs_cache_get(), outputting "SQUASHFS
> > error: Unable to read metadata cache entry [6fa]" in the syz log.
> >
> 
> NO, *that* is caused by the failure to read some other inodes which
> as a result are correctly not created.  Nothing to do with the oops here.
> 
> > [Fix]
> > Before performing a read ahead operation in squashfs_read_folio() and
> > squashfs_readahead(), check if i_size is not 0 before continuing.
> >
> 
> A third NO, it is only 0 because the variable overflowed.
> 
> Additionally, let's look at your "fix" here.
> 
> > @@ -461,6 +461,11 @@ static int squashfs_read_folio(struct file *file, struct folio *folio)
> >  	TRACE("Entered squashfs_readpage, page index %lx, start block %llx\n",
> >  				page->index, squashfs_i(inode)->start);
> >
> > +	if (!file_end) {
> > +		res = -EINVAL;
> > +		goto out;
> > +	}
> > +
> 
> file_end is computed by
> 
> 	int file_end = i_size_read(inode) >> msblk->block_log;
> 
> So your "fix" will reject *any* file less than msblk->block_log in
> size as invalid, including perfectly valid zero size files (empty
> files are valid too).

edward