• Ye Bin's avatar
    ext4: fix use-after-free read in ext4_find_extent for bigalloc + inline · 83565959
    Ye Bin authored
    Syzbot found the following issue:
    loop0: detected capacity change from 0 to 2048
    EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 without journal. Quota mode: none.
    ==================================================================
    BUG: KASAN: use-after-free in ext4_ext_binsearch_idx fs/ext4/extents.c:768 [inline]
    BUG: KASAN: use-after-free in ext4_find_extent+0x76e/0xd90 fs/ext4/extents.c:931
    Read of size 4 at addr ffff888073644750 by task syz-executor420/5067
    
    CPU: 0 PID: 5067 Comm: syz-executor420 Not tainted 6.2.0-rc1-syzkaller #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
    Call Trace:
     <TASK>
     __dump_stack lib/dump_stack.c:88 [inline]
     dump_stack_lvl+0x1b1/0x290 lib/dump_stack.c:106
     print_address_description+0x74/0x340 mm/kasan/report.c:306
     print_report+0x107/0x1f0 mm/kasan/report.c:417
     kasan_report+0xcd/0x100 mm/kasan/report.c:517
     ext4_ext_binsearch_idx fs/ext4/extents.c:768 [inline]
     ext4_find_extent+0x76e/0xd90 fs/ext4/extents.c:931
     ext4_clu_mapped+0x117/0x970 fs/ext4/extents.c:5809
     ext4_insert_delayed_block fs/ext4/inode.c:1696 [inline]
     ext4_da_map_blocks fs/ext4/inode.c:1806 [inline]
     ext4_da_get_block_prep+0x9e8/0x13c0 fs/ext4/inode.c:1870
     ext4_block_write_begin+0x6a8/0x2290 fs/ext4/inode.c:1098
     ext4_da_write_begin+0x539/0x760 fs/ext4/inode.c:3082
     generic_perform_write+0x2e4/0x5e0 mm/filemap.c:3772
     ext4_buffered_write_iter+0x122/0x3a0 fs/ext4/file.c:285
     ext4_file_write_iter+0x1d0/0x18f0
     call_write_iter include/linux/fs.h:2186 [inline]
     new_sync_write fs/read_write.c:491 [inline]
     vfs_write+0x7dc/0xc50 fs/read_write.c:584
     ksys_write+0x177/0x2a0 fs/read_write.c:637
     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+0x63/0xcd
    RIP: 0033:0x7f4b7a9737b9
    RSP: 002b:00007ffc5cac3668 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
    RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f4b7a9737b9
    RDX: 00000000175d9003 RSI: 0000000020000200 RDI: 0000000000000004
    RBP: 00007f4b7a933050 R08: 0000000000000000 R09: 0000000000000000
    R10: 000000000000079f R11: 0000000000000246 R12: 00007f4b7a9330e0
    R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
     </TASK>
    
    Above issue is happens when enable bigalloc and inline data feature. As
    commit 131294c3 fixed delayed allocation bug in ext4_clu_mapped for
    bigalloc + inline. But it only resolved issue when has inline data, if
    inline data has been converted to extent(ext4_da_convert_inline_data_to_extent)
    before writepages, there is no EXT4_STATE_MAY_INLINE_DATA flag. However
    i_data is still store inline data in this scene. Then will trigger UAF
    when find extent.
    To resolve above issue, there is need to add judge "ext4_has_inline_data(inode)"
    in ext4_clu_mapped().
    
    Fixes: 131294c3 ("ext4: fix delayed allocation bug in ext4_clu_mapped for bigalloc + inline")
    Reported-by: syzbot+bf4bb7731ef73b83a3b4@syzkaller.appspotmail.com
    Reviewed-by: default avatarJan Kara <jack@suse.cz>
    Reviewed-by: default avatarYe Bin <yebin10@huawei.com>
    Reviewed-by: default avatarTudor Ambarus <tudor.ambarus@linaro.org>
    Tested-by: default avatarTudor Ambarus <tudor.ambarus@linaro.org>
    Link: https://lore.kernel.org/r/20230406111627.1916759-1-tudor.ambarus@linaro.orgSigned-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
    83565959
extents.c 166 KB