ext4: store maxbytes for bitmapped files and return EFBIG as appropriate

Calculate & store the max offset for bitmapped files, and
catch too-large seeks, truncates, and writes in ext4, shortening
or rejecting as appropriate.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>

1 files changed, 18 insertions, 1 deletions

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 1a81cd66d63b..a6b2aa14626e 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -56,8 +56,25 @@ ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
         ssize_t ret;
         int err;
 
-        ret = generic_file_aio_write(iocb, iov, nr_segs, pos);
+        /*
+         * If we have encountered a bitmap-format file, the size limit
+         * is smaller than s_maxbytes, which is for extent-mapped files.
+         */
+
+        if (!(EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL)) {
+                struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+                size_t length = iov_length(iov, nr_segs);
 
+                if (pos > sbi->s_bitmap_maxbytes)
+                        return -EFBIG;
+
+                if (pos + length > sbi->s_bitmap_maxbytes) {
+                        nr_segs = iov_shorten((struct iovec *)iov, nr_segs,
+                                              sbi->s_bitmap_maxbytes - pos);
+                }
+        }
+
+        ret = generic_file_aio_write(iocb, iov, nr_segs, pos);
         /*
          * Skip flushing if there was an error, or if nothing was written.
          */