| From f70749ca42943faa4d4dcce46dfdcaadb1d0c4b6 Mon Sep 17 00:00:00 2001 |
| From: Vegard Nossum <vegard.nossum@oracle.com> |
| Date: Thu, 30 Jun 2016 11:53:46 -0400 |
| Subject: ext4: check for extents that wrap around |
| |
| From: Vegard Nossum <vegard.nossum@oracle.com> |
| |
| commit f70749ca42943faa4d4dcce46dfdcaadb1d0c4b6 upstream. |
| |
| An extent with lblock = 4294967295 and len = 1 will pass the |
| ext4_valid_extent() test: |
| |
| ext4_lblk_t last = lblock + len - 1; |
| |
| if (len == 0 || lblock > last) |
| return 0; |
| |
| since last = 4294967295 + 1 - 1 = 4294967295. This would later trigger |
| the BUG_ON(es->es_lblk + es->es_len < es->es_lblk) in ext4_es_end(). |
| |
| We can simplify it by removing the - 1 altogether and changing the test |
| to use lblock + len <= lblock, since now if len = 0, then lblock + 0 == |
| lblock and it fails, and if len > 0 then lblock + len > lblock in order |
| to pass (i.e. it doesn't overflow). |
| |
| Fixes: 5946d0893 ("ext4: check for overlapping extents in ext4_valid_extent_entries()") |
| Fixes: 2f974865f ("ext4: check for zero length extent explicitly") |
| Cc: Eryu Guan <guaneryu@gmail.com> |
| Signed-off-by: Phil Turnbull <phil.turnbull@oracle.com> |
| Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com> |
| Signed-off-by: Theodore Ts'o <tytso@mit.edu> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| fs/ext4/extents.c | 8 ++++++-- |
| 1 file changed, 6 insertions(+), 2 deletions(-) |
| |
| --- a/fs/ext4/extents.c |
| +++ b/fs/ext4/extents.c |
| @@ -376,9 +376,13 @@ static int ext4_valid_extent(struct inod |
| ext4_fsblk_t block = ext4_ext_pblock(ext); |
| int len = ext4_ext_get_actual_len(ext); |
| ext4_lblk_t lblock = le32_to_cpu(ext->ee_block); |
| - ext4_lblk_t last = lblock + len - 1; |
| |
| - if (len == 0 || lblock > last) |
| + /* |
| + * We allow neither: |
| + * - zero length |
| + * - overflow/wrap-around |
| + */ |
| + if (lblock + len <= lblock) |
| return 0; |
| return ext4_data_block_valid(EXT4_SB(inode->i_sb), block, len); |
| } |