lkml.org 
[lkml]   [2019]   [Jan]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.14 22/27] ext4: fix a potential fiemap/page fault deadlock w/ inline_data
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Theodore Ts'o <tytso@mit.edu>

commit 2b08b1f12cd664dc7d5c84ead9ff25ae97ad5491 upstream.

The ext4_inline_data_fiemap() function calls fiemap_fill_next_extent()
while still holding the xattr semaphore. This is not necessary and it
triggers a circular lockdep warning. This is because
fiemap_fill_next_extent() could trigger a page fault when it writes
into page which triggers a page fault. If that page is mmaped from
the inline file in question, this could very well result in a
deadlock.

This problem can be reproduced using generic/519 with a file system
configuration which has the inline_data feature enabled.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/ext4/inline.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/fs/ext4/inline.c
+++ b/fs/ext4/inline.c
@@ -1864,12 +1864,12 @@ int ext4_inline_data_fiemap(struct inode
physical += (char *)ext4_raw_inode(&iloc) - iloc.bh->b_data;
physical += offsetof(struct ext4_inode, i_block);

- if (physical)
- error = fiemap_fill_next_extent(fieinfo, start, physical,
- inline_len, flags);
brelse(iloc.bh);
out:
up_read(&EXT4_I(inode)->xattr_sem);
+ if (physical)
+ error = fiemap_fill_next_extent(fieinfo, start, physical,
+ inline_len, flags);
return (error < 0 ? error : 0);
}


\
 
 \ /
  Last update: 2019-01-15 17:40    [W:0.167 / U:14.368 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site