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authorJan Kara <jack@suse.cz>2018-05-12 19:55:00 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-06-26 08:08:07 +0800
commit42cc42eabafb6bd4e5ea4cbde72f7fb4d24cc7bd (patch)
treef578b10d7d8e97b26f45a05161c81a49068e6bd8
parent2435d6b11057c8b02d6a8932501cb980c23e2d05 (diff)
ext4: fix hole length detection in ext4_ind_map_blocks()
commit 2ee3ee06a8fd792765fa3267ddf928997797eec5 upstream. When ext4_ind_map_blocks() computes a length of a hole, it doesn't count with the fact that mapped offset may be somewhere in the middle of the completely empty subtree. In such case it will return too large length of the hole which then results in lseek(SEEK_DATA) to end up returning an incorrect offset beyond the end of the hole. Fix the problem by correctly taking offset within a subtree into account when computing a length of a hole. Fixes: facab4d9711e7aa3532cb82643803e8f1b9518e8 CC: stable@vger.kernel.org Reported-by: Jeff Mahoney <jeffm@suse.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/ext4/indirect.c14
1 files changed, 10 insertions, 4 deletions
diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index bc15c2c17633..58229c1b4a3d 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -560,10 +560,16 @@ int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
unsigned epb = inode->i_sb->s_blocksize / sizeof(u32);
int i;
- /* Count number blocks in a subtree under 'partial' */
- count = 1;
- for (i = 0; partial + i != chain + depth - 1; i++)
- count *= epb;
+ /*
+ * Count number blocks in a subtree under 'partial'. At each
+ * level we count number of complete empty subtrees beyond
+ * current offset and then descend into the subtree only
+ * partially beyond current offset.
+ */
+ count = 0;
+ for (i = partial - chain + 1; i < depth; i++)
+ count = count * epb + (epb - offsets[i] - 1);
+ count++;
/* Fill in size of a hole we found */
map->m_pblk = 0;
map->m_len = min_t(unsigned int, map->m_len, count);