| Message ID | 1467239688-2588-1-git-send-email-vegard.nossum@oracle.com |
|---|---|
| State | Awaiting Upstream, archived |
| Headers | show |
On Thu, Jun 30, 2016 at 12:34:48AM +0200, Vegard Nossum wrote: > 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> > Cc: stable@vger.kernel.org > Signed-off-by: Phil Turnbull <phil.turnbull@oracle.com> > Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com> Thanks, applied. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 2a2eef9..2f258c6 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -381,9 +381,13 @@ static int ext4_valid_extent(struct inode *inode, struct ext4_extent *ext) 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); }
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> Cc: stable@vger.kernel.org Signed-off-by: Phil Turnbull <phil.turnbull@oracle.com> Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com> --- fs/ext4/extents.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)