omfs: fix oops when file metadata is corrupted
A fuzzed fileystem image failed with OMFS when the extent count was
used in a loop without being checked against the max number of extents.
It also provoked a signed division for an array index that was checked
as if unsigned, leading to index by -1.
omfsck will be updated to fix these cases, in the meantime bail out
gracefully.
Reported-by: Eric Sesterhenn <snakebyte@gmx.de>
Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/omfs/bitmap.c b/fs/omfs/bitmap.c
index 697663b..e1c0ec0 100644
--- a/fs/omfs/bitmap.c
+++ b/fs/omfs/bitmap.c
@@ -92,7 +92,7 @@
struct buffer_head *bh;
struct omfs_sb_info *sbi = OMFS_SB(sb);
int bits_per_entry = 8 * sb->s_blocksize;
- int map, bit;
+ unsigned int map, bit;
int ret = 0;
u64 tmp;
@@ -176,7 +176,8 @@
struct omfs_sb_info *sbi = OMFS_SB(sb);
int bits_per_entry = 8 * sb->s_blocksize;
u64 tmp;
- int map, bit, ret;
+ unsigned int map, bit;
+ int ret;
tmp = block;
bit = do_div(tmp, bits_per_entry);
diff --git a/fs/omfs/file.c b/fs/omfs/file.c
index 7e24990..834b233 100644
--- a/fs/omfs/file.c
+++ b/fs/omfs/file.c
@@ -26,6 +26,13 @@
return err ? -EIO : 0;
}
+static u32 omfs_max_extents(struct omfs_sb_info *sbi, int offset)
+{
+ return (sbi->s_sys_blocksize - offset -
+ sizeof(struct omfs_extent)) /
+ sizeof(struct omfs_extent_entry) + 1;
+}
+
void omfs_make_empty_table(struct buffer_head *bh, int offset)
{
struct omfs_extent *oe = (struct omfs_extent *) &bh->b_data[offset];
@@ -45,6 +52,7 @@
struct buffer_head *bh;
u64 next, last;
u32 extent_count;
+ u32 max_extents;
int ret;
/* traverse extent table, freeing each entry that is greater
@@ -62,15 +70,18 @@
goto out;
oe = (struct omfs_extent *)(&bh->b_data[OMFS_EXTENT_START]);
+ max_extents = omfs_max_extents(sbi, OMFS_EXTENT_START);
for (;;) {
- if (omfs_is_bad(sbi, (struct omfs_header *) bh->b_data, next)) {
- brelse(bh);
- goto out;
- }
+ if (omfs_is_bad(sbi, (struct omfs_header *) bh->b_data, next))
+ goto out_brelse;
extent_count = be32_to_cpu(oe->e_extent_count);
+
+ if (extent_count > max_extents)
+ goto out_brelse;
+
last = next;
next = be64_to_cpu(oe->e_next);
entry = &oe->e_entry;
@@ -98,10 +109,14 @@
if (!bh)
goto out;
oe = (struct omfs_extent *) (&bh->b_data[OMFS_EXTENT_CONT]);
+ max_extents = omfs_max_extents(sbi, OMFS_EXTENT_CONT);
}
ret = 0;
out:
return ret;
+out_brelse:
+ brelse(bh);
+ return ret;
}
static void omfs_truncate(struct inode *inode)
@@ -154,9 +169,7 @@
goto out;
}
}
- max_count = (sbi->s_sys_blocksize - OMFS_EXTENT_START -
- sizeof(struct omfs_extent)) /
- sizeof(struct omfs_extent_entry) + 1;
+ max_count = omfs_max_extents(sbi, OMFS_EXTENT_START);
/* TODO: add a continuation block here */
if (be32_to_cpu(oe->e_extent_count) > max_count-1)
@@ -225,6 +238,7 @@
sector_t next, offset;
int ret;
u64 new_block;
+ u32 max_extents;
int extent_count;
struct omfs_extent *oe;
struct omfs_extent_entry *entry;
@@ -238,6 +252,7 @@
goto out;
oe = (struct omfs_extent *)(&bh->b_data[OMFS_EXTENT_START]);
+ max_extents = omfs_max_extents(sbi, OMFS_EXTENT_START);
next = inode->i_ino;
for (;;) {
@@ -249,6 +264,9 @@
next = be64_to_cpu(oe->e_next);
entry = &oe->e_entry;
+ if (extent_count > max_extents)
+ goto out_brelse;
+
offset = find_block(inode, entry, block, extent_count, &remain);
if (offset > 0) {
ret = 0;
@@ -266,6 +284,7 @@
if (!bh)
goto out;
oe = (struct omfs_extent *) (&bh->b_data[OMFS_EXTENT_CONT]);
+ max_extents = omfs_max_extents(sbi, OMFS_EXTENT_CONT);
}
if (create) {
ret = omfs_grow_extent(inode, oe, &new_block);