From: Zhihao Cheng chengzhihao1@huawei.com
maillist inclusion category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I6SMBI CVE: NA
Reference: https://www.spinics.net/lists/linux-ext4/msg88386.html
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Following process makes i_disksize exceed i_size:
generic_perform_write copied = iov_iter_copy_from_user_atomic(len) // copied < len ext4_da_write_end | ext4_update_i_disksize | new_i_size = pos + copied; | WRITE_ONCE(EXT4_I(inode)->i_disksize, newsize) // update i_disksize | generic_write_end | copied = block_write_end(copied, len) // copied = 0 | if (unlikely(copied < len)) | if (!PageUptodate(page)) | copied = 0; | if (pos + copied > inode->i_size) // return false if (unlikely(copied == 0)) goto again; if (unlikely(iov_iter_fault_in_readable(i, bytes))) { status = -EFAULT; break; }
We get i_disksize greater than i_size here, which could trigger WARNING check 'i_size_read(inode) < EXT4_I(inode)->i_disksize' while doing dio:
ext4_dio_write_iter iomap_dio_rw __iomap_dio_rw // return err, length is not aligned to 512 ext4_handle_inode_extension WARN_ON_ONCE(i_size_read(inode) < EXT4_I(inode)->i_disksize) // Oops
WARNING: CPU: 2 PID: 2609 at fs/ext4/file.c:319 CPU: 2 PID: 2609 Comm: aa Not tainted 6.3.0-rc2 RIP: 0010:ext4_file_write_iter+0xbc7 Call Trace: vfs_write+0x3b1 ksys_write+0x77 do_syscall_64+0x39
Fix it by updating 'copied' value before updating i_disksize just like ext4_write_inline_data_end() does.
Fetch a reproducer in [Link].
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217209 Fixes: 64769240bd07 ("ext4: Add delayed allocation support in data=writeback mode") Signed-off-by: Zhihao Cheng chengzhihao1@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Yongqiang Liu liuyongqiang13@huawei.com --- fs/ext4/inode.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 336761400f7a..b327fde0225a 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3147,6 +3147,9 @@ static int ext4_da_write_end(struct file *file, ext4_has_inline_data(inode)) return ext4_write_inline_data_end(inode, pos, len, copied, page);
+ if (unlikely(copied < len) && !PageUptodate(page)) + copied = 0; + start = pos & (PAGE_SIZE - 1); end = start + copied - 1;