[PATCH] rock.c: handle corrupted directories

The bug in rock.c is that it's totally trusting of the contents of the
directories.  If the directory says there's a continuation 10000 bytes into
this 4k block then we cheerily poke around in memory we don't own and oops.

So change rock_continue() to apply various sanity checks, at least ensuring
that the offset+length remain within the bounds for the header part of a
struct rock_ridge directory entry.

Note that the kernel can still overindex the buffer due to the variable size
of the rock-ridge directory entries.  We cannot check that in rock_continue()
unless we go parse the directory entry's signature and work out its size.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/fs/isofs/rock.c b/fs/isofs/rock.c
index 977dd7009c07..9a81830abff8 100644
--- a/fs/isofs/rock.c
+++ b/fs/isofs/rock.c
@@ -81,9 +81,22 @@ static void init_rock_state(struct rock_state *rs, struct inode *inode)
 static int rock_continue(struct rock_state *rs)
 {
         int ret = 1;
+        int blocksize = 1 << rs->inode->i_blkbits;
+        const int min_de_size = offsetof(struct rock_ridge, u);
 
         kfree(rs->buffer);
         rs->buffer = NULL;
+
+        if ((unsigned)rs->cont_offset > blocksize - min_de_size ||
+            (unsigned)rs->cont_size > blocksize ||
+            (unsigned)(rs->cont_offset + rs->cont_size) > blocksize) {
+                printk(KERN_NOTICE "rock: corrupted directory entry. "
+                        "extent=%d, offset=%d, size=%d\n",
+                        rs->cont_extent, rs->cont_offset, rs->cont_size);
+                ret = -EIO;
+                goto out;
+        }
+
         if (rs->cont_extent) {
                 struct buffer_head *bh;