[U-Boot] [PATCH] fs: btrfs: fix btrfs_search_tree invalid results

[U-Boot] [PATCH] fs: btrfs: fix btrfs_search_tree invalid results

[Pierre Bourdon]

btrfs_search_tree should return the first item in the tree that is
greater or equal to the searched item.

The search algorithm did not properly handle the edge case where the
searched item is higher than the last item of the node but lower than
the first item of the next node. Instead of properly returning the first
item of the next node, it was returning an invalid path pointer
(pointing to a non-existent item after the last item of the node + 1).

This fixes two issues in the btrfs driver:
  - Looking for a ROOT_ITEM could fail if it was the first item of its
    leaf node.
  - Iterating through DIR_INDEX entries (for readdir) could fail if the
    first DIR_INDEX entry was the first item of a leaf node.

Signed-off-by: Pierre Bourdon <delroth@gmail.com>
Cc: Marek Behun <marek.behun@nic.cz>
---
 fs/btrfs/ctree.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index d248d79932..55246ea0fc 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -187,8 +187,13 @@ int btrfs_search_tree(const struct btrfs_root *root, struct btrfs_key *key,
 
 		if (lvl)
 			logical = buf->node.ptrs[slot].blockptr;
-		else
+		else {
+			/* cur leaf max < searched value < next leaf min */
+			if (slot >= buf->header.nritems)
+				if (btrfs_next_slot(p) < 0)
+					goto err;
 			break;
+		}
 	}
 
 	return 0;
-- 
2.19.2

[U-Boot] [PATCH] fs: btrfs: fix btrfs_search_tree invalid results

[Marek Behun]

Hi Pierre

On Mon, 15 Apr 2019 03:30:32 +0200
Pierre Bourdon <delroth@gmail.com> wrote:

> btrfs_search_tree should return the first item in the tree that is
> greater or equal to the searched item.
> 
> The search algorithm did not properly handle the edge case where the
> searched item is higher than the last item of the node but lower than
> the first item of the next node. Instead of properly returning the first
> item of the next node, it was returning an invalid path pointer
> (pointing to a non-existent item after the last item of the node + 1).
> 
> This fixes two issues in the btrfs driver:
>   - Looking for a ROOT_ITEM could fail if it was the first item of its
>     leaf node.
>   - Iterating through DIR_INDEX entries (for readdir) could fail if the
>     first DIR_INDEX entry was the first item of a leaf node.
> 
> Signed-off-by: Pierre Bourdon <delroth@gmail.com>
> Cc: Marek Behun <marek.behun@nic.cz>
> ---
>  fs/btrfs/ctree.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
> index d248d79932..55246ea0fc 100644
> --- a/fs/btrfs/ctree.c
> +++ b/fs/btrfs/ctree.c
> @@ -187,8 +187,13 @@ int btrfs_search_tree(const struct btrfs_root *root, struct btrfs_key *key,
>  
>  		if (lvl)
>  			logical = buf->node.ptrs[slot].blockptr;
> -		else
> +		else {
> +			/* cur leaf max < searched value < next leaf min */
> +			if (slot >= buf->header.nritems)
> +				if (btrfs_next_slot(p) < 0)
> +					goto err;
>  			break;
> +		}

Hi Pierre, if you are adding { } braces to else, please add them to the
if also. Also comment that you are correcting for invalid slot value.

		if (lvl) {
			logical = buf->node.ptrs[slot].blockptr;
		} else {
			/*
			 * Slot can have invalid value if
			 * current leaf max < searched value < next leaf min.
			 * Jump to next in this case.
			 */
			if (slot >= buf->header.nritems)
				if (btrfs_next_slot(p) < 0)
					goto err;
			break;
		}

Otherwise thanks, I encountered some problems a once or twice but
didn't have time to investigate.

Marek