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authorVegard Nossum <vegard.nossum@oracle.com>2016-06-30 11:53:46 -0400
committerTheodore Ts'o <tytso@mit.edu>2016-06-30 11:53:46 -0400
commitf70749ca42943faa4d4dcce46dfdcaadb1d0c4b6 (patch)
treef4f3877c9b353fb99102c10f9ac200739bb94e97 /fs/ext4/extents.c
parentabcfb5d979892fc8b12574551fc907c05fe1b11b (diff)
downloadlinux-f70749ca42943faa4d4dcce46dfdcaadb1d0c4b6.tar.bz2
ext4: check for extents that wrap around
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> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ext4/extents.c')
-rw-r--r--fs/ext4/extents.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 2a2eef9c14e4..2f258c68d3e0 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);
}