| Message ID | 1397050714-14132-1-git-send-email-fdmanana@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c index 9d84658..0721113 100644 --- a/fs/btrfs/file-item.c +++ b/fs/btrfs/file-item.c @@ -749,7 +749,7 @@ again: int slot = path->slots[0] + 1; /* we didn't find a csum item, insert one */ nritems = btrfs_header_nritems(path->nodes[0]); - if (path->slots[0] >= nritems - 1) { + if (!nritems || (path->slots[0] >= nritems - 1)) { ret = btrfs_next_leaf(root, path); if (ret == 1) found_next = 1;
When the csum tree is empty, our leaf (path->nodes[0]) has a number of items equal to 0 and since btrfs_header_nritems() returns an unsigned integer (and so is our local nritems variable) the following comparison always evaluates to false: if (path->slots[0] >= nritems - 1) { As the casting rules lead to: if ((u32)0 >= (u32)4294967295) { This makes us access key at slot paths->slots[0] + 1 (1) of the empty leaf some lines below: btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot); if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID || found_key.type != BTRFS_EXTENT_CSUM_KEY) { found_next = 1; goto insert; } So just don't access such non-existent slot and don't set found_next to 1 when the tree is empty. It's very unlikely we'll get a random key with the objectid and type values above, which is where we could go into trouble. If nritems is 0, just set found_next to 1 anyway as it will make us insert a csum item covering our whole extent (or the whole leaf) when the tree is empty. Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com> --- fs/btrfs/file-item.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)