Re: Fw: [syzbot] KASAN: use-after-free Read in copy_page_from_iter_atomic

Re: Fw: [syzbot] KASAN: use-after-free Read in copy_page_from_iter_atomic

[Dave Kleikamp]

On 9/19/21 18:19, Andrew Morton wrote:
> might be a loop-vs-jfs thing?

It may be just a buggy, rarely-taken error path in jfs_fill_super that 
happened to get caught in the loop code. I'll have to dig through this.

Shaggy

> 
> Begin forwarded message:
> 
> Date: Fri, 17 Sep 2021 09:33:28 -0700
> From: syzbot <syzbot+ffc4eceb22dfcf9fd6a0@syzkaller.appspotmail.com>
> To: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com
> Subject: [syzbot] KASAN: use-after-free Read in copy_page_from_iter_atomic
> 
> 
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    7d2a07b76933 Linux 5.14
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=12fe8af5300000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=113c5df900d8cf12
> dashboard link: https://syzkaller.appspot.com/bug?extid=ffc4eceb22dfcf9fd6a0
> compiler:       Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+ffc4eceb22dfcf9fd6a0@syzkaller.appspotmail.com
> 
> ==================================================================
> BUG: KASAN: use-after-free in copy_page_from_iter_atomic+0x9c7/0x1520 lib/iov_iter.c:918
> Read of size 4096 at addr ffff8880298b0000 by task kworker/u4:8/11701
> 
> CPU: 0 PID: 11701 Comm: kworker/u4:8 Not tainted 5.14.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Workqueue: loop5 loop_rootcg_workfn
> 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+0x25/0x60 mm/kasan/shadow.c:65
>   copy_page_from_iter_atomic+0x9c7/0x1520 lib/iov_iter.c:918
>   generic_perform_write+0x2dd/0x580 mm/filemap.c:3664
>   __generic_file_write_iter+0x225/0x5a0 mm/filemap.c:3783
>   generic_file_write_iter+0xa7/0x1b0 mm/filemap.c:3815
>   do_iter_readv_writev+0x566/0x770 include/linux/fs.h:2108
>   do_iter_write+0x16c/0x5f0 fs/read_write.c:866
>   lo_write_bvec+0x267/0x6f0 drivers/block/loop.c:328
>   lo_write_simple drivers/block/loop.c:350 [inline]
>   do_req_filebacked drivers/block/loop.c:668 [inline]
>   loop_handle_cmd drivers/block/loop.c:2204 [inline]
>   loop_process_work+0x21c2/0x2cc0 drivers/block/loop.c:2244
>   process_one_work+0x833/0x10c0 kernel/workqueue.c:2276
>   worker_thread+0xac1/0x1320 kernel/workqueue.c:2422
>   kthread+0x453/0x480 kernel/kthread.c:319
>   ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> 
> The buggy address belongs to the page:
> page:ffffea0000a62c00 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x298b0
> flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
> raw: 00fff00000000000 ffffea0000bb3348 ffffea0000d492c8 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 0xdc0(GFP_KERNEL|__GFP_ZERO), pid 20552, ts 462739681694, free_ts 462770335978
>   prep_new_page mm/page_alloc.c:2436 [inline]
>   get_page_from_freelist+0x779/0xa30 mm/page_alloc.c:4168
>   __alloc_pages+0x26c/0x5f0 mm/page_alloc.c:5390
>   lbmLogInit fs/jfs/jfs_logmgr.c:1824 [inline]
>   lmLogInit+0x2fc/0x1e90 fs/jfs/jfs_logmgr.c:1278
>   open_inline_log fs/jfs/jfs_logmgr.c:1183 [inline]
>   lmLogOpen+0x505/0x1190 fs/jfs/jfs_logmgr.c:1077
>   jfs_mount_rw+0xe7/0x710 fs/jfs/jfs_mount.c:260
>   jfs_fill_super+0x64c/0xc20 fs/jfs/super.c:570
>   mount_bdev+0x26c/0x3a0 fs/super.c:1368
>   legacy_get_tree+0xea/0x180 fs/fs_context.c:610
>   vfs_get_tree+0x86/0x270 fs/super.c:1498
>   do_new_mount fs/namespace.c:2923 [inline]
>   path_mount+0x1981/0x2c10 fs/namespace.c:3253
>   do_mount fs/namespace.c:3266 [inline]
>   __do_sys_mount fs/namespace.c:3474 [inline]
>   __se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3451
>   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
> page last free stack trace:
>   reset_page_owner include/linux/page_owner.h:24 [inline]
>   free_pages_prepare mm/page_alloc.c:1346 [inline]
>   free_pcp_prepare+0xc29/0xd20 mm/page_alloc.c:1397
>   free_unref_page_prepare mm/page_alloc.c:3332 [inline]
>   free_unref_page+0x7e/0x550 mm/page_alloc.c:3411
>   lbmLogShutdown fs/jfs/jfs_logmgr.c:1872 [inline]
>   lmLogShutdown+0x4ad/0x920 fs/jfs/jfs_logmgr.c:1692
>   lmLogClose+0x2c2/0x560 fs/jfs/jfs_logmgr.c:1468
>   jfs_umount+0x297/0x370 fs/jfs/jfs_umount.c:116
>   jfs_fill_super+0x8e5/0xc20 fs/jfs/super.c:605
>   mount_bdev+0x26c/0x3a0 fs/super.c:1368
>   legacy_get_tree+0xea/0x180 fs/fs_context.c:610
>   vfs_get_tree+0x86/0x270 fs/super.c:1498
>   do_new_mount fs/namespace.c:2923 [inline]
>   path_mount+0x1981/0x2c10 fs/namespace.c:3253
>   do_mount fs/namespace.c:3266 [inline]
>   __do_sys_mount fs/namespace.c:3474 [inline]
>   __se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3451
>   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
> 
> Memory state around the buggy address:
>   ffff8880298aff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>   ffff8880298aff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> ffff8880298b0000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>                     ^
>   ffff8880298b0080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>   ffff8880298b0100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> ==================================================================
> 
> 
> ---
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