Re: [PATCH] btrfs: avoid using fixed char array size for tree names

[Sam James <sam@gentoo.org>]

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Qu Wenruo <wqu@suse.com> writes:

> [BUG]
> There is a bug report that using the latest trunk GCC, btrfs would cause
> unterminated-string-initialization warning:
>
>   linux-6.6/fs/btrfs/print-tree.c:29:49: error: initializer-string for array of ‘char’ is too long [-Werror=unterminated-string-initialization]
>    29 |         { BTRFS_BLOCK_GROUP_TREE_OBJECTID,      "BLOCK_GROUP_TREE"      },
>       |
>       ^~~~~~~~~~~~~~~~~~
>
> [CAUSE]
> To print tree names we have an array of root_name_map structure, which
> uses "char name[16];" to store the name string of a tree.
>
> But the following trees have names exactly at 16 chars length:
> - "BLOCK_GROUP_TREE"
> - "RAID_STRIPE_TREE"
>
> This means we will have no space for the terminating '\0', and can lead
> to unexpected access when printing the name.
>
> [FIX]
> Instead of "char name[16];" use "const char *" instead.
>
> Since the name strings are all read-only data, and are all NULL
> terminated by default, there is not much need to bother the length at
> all.
>
> Reported-by: Sam James <sam@gentoo.org>
> Signed-off-by: Qu Wenruo <wqu@suse.com>

Thank you for the quick fix! I agree that this seems like the cleanest
change.

Tested-by: Sam James <sam@gentoo.org>

> ---
>  fs/btrfs/print-tree.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/print-tree.c b/fs/btrfs/print-tree.c
> index 32dcea662da3..fc821aa446f0 100644
> --- a/fs/btrfs/print-tree.c
> +++ b/fs/btrfs/print-tree.c
> @@ -14,7 +14,7 @@
>  
>  struct root_name_map {
>  	u64 id;
> -	char name[16];
> +	const char *name;
>  };
>  
>  static const struct root_name_map root_map[] = {

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