fuse2fs: fix readlink failure

For readlink of slow symlinks, an IO error when reading the link target
cause memory corruption.  This happens because the error case for
ext2fs_file_read closes the file, translates the error, but then jumps
down to the regular termination code, which re-closes the file and is
hence a UAF.  Straighten out the error paths to eliminate the UAF.
Also fix the bug that short target reads aren't flagged as corruption
as is done in the kernel.

Cc: <linux-ext4@vger.kernel.org> # v1.43
Fixes: 81cbf1ef4f5dab ("misc: add fuse2fs, a FUSE server for e2fsprogs")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>

diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c
index 4d42a634bf377b7dd60ddadfa085134e82584e67..f9da9c1ac051cb3a4c30b0a7f0160d99c48023cb 100644 (file)
--- a/misc/fuse2fs.c
+++ b/misc/fuse2fs.c
@@ -1086,13 +1086,11 @@ static int op_readlink(const char *path, char *buf, size_t len)
                }
 
                err = ext2fs_file_read(file, buf, len, &got);
-               if (err || got != len) {
-                       ext2fs_file_close(file);
+               if (err)
                        ret = translate_error(fs, ino, err);
-                       goto out2;
-               }
+               else if (got != len)
+                       ret = translate_error(fs, ino, EXT2_ET_INODE_CORRUPTED);
 
-out2:
                err = ext2fs_file_close(file);
                if (ret)
                        goto out;