fs: btrfs: fix out of bounds write

Fix btrfs_read/read_and_truncate_page write out of bounds of destination
buffer. Old behavior break bootstd malloc'd buffers of exact file size.
Previously this OOB write have not been noticed because distroboot usually
read files into huge static memory areas.

Signed-off-by: Alex Shumsky <alexthreed@gmail.com>
Fixes: e342718 ("fs: btrfs: Implement btrfs_file_read()")
Reviewed-by: Qu Wenruo <wqu@suse.com>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 4691612eda338589ec803d93a7a017f20bd9838b..3998ffc2c81957d16d15896b50e3c2fe3bb6b4c1 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -640,7 +640,11 @@ static int read_and_truncate_page(struct btrfs_path *path,
        extent_type = btrfs_file_extent_type(leaf, fi);
        if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                ret = btrfs_read_extent_inline(path, fi, buf);
-               memcpy(dest, buf + page_off, min(page_len, ret));
+               if (ret < 0) {
+                       free(buf);
+                       return ret;
+               }
+               memcpy(dest, buf + page_off, min3(page_len, ret, len));
                free(buf);
                return len;
        }
@@ -652,7 +656,7 @@ static int read_and_truncate_page(struct btrfs_path *path,
                free(buf);
                return ret;
        }
-       memcpy(dest, buf + page_off, page_len);
+       memcpy(dest, buf + page_off, min(page_len, len));
        free(buf);
        return len;
 }