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authorVegard Nossum <vegard.nossum@oracle.com>2016-06-30 11:53:46 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-08-16 09:29:03 +0200
commitbe6acbd7311504ded04b25edae2c250346dec6f2 (patch)
tree6b5edd8d236bce3eec54c5d07492604a22e5821c
parent29c8e05930bc27761ab957acd0786951bad8ec75 (diff)
ext4: check for extents that wrap around
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>
-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 a3be02e03021..0bffd9a0fbf2 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -359,9 +359,13 @@ 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);
}