[PATCH] 9p: Add const and unsigned to wnames allocation type

[PATCH] 9p: Add const and unsigned to wnames allocation type

[Kees Cook]

From: Kees Cook <kees+treewide@kernel.org>

In preparation for converting the kmalloc family of allocators to the
type-aware kmalloc_obj family, we need to make sure that the returned
type from the allocation matches the type of the variable being
assigned. (The kmalloc family returns "void *", which can be implicitly
cast to any pointer type.)

The assigned type is "const unsigned char **", but the converted
allocation type would be "char **", which differs in both the const
qualifier and the signedness of the character type. Take the size from
the assignment target instead. No change in allocation size results.

Build tested ARCH=x86_64 allmodconfig with GCC 16.2.0:
fs/9p/fid.o

Assisted-by: LLM coccinelle
Signed-off-by: Kees Cook <kees+treewide@kernel.org>
---
Cc: Eric Van Hensbergen <ericvh@kernel.org>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Christian Schoenebeck <linux_oss@crudebyte.com>
Cc: <v9fs@lists.linux.dev>
---
 fs/9p/fid.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/9p/fid.c b/fs/9p/fid.c
index 76242d450aa7..65dc7972b396 100644
--- a/fs/9p/fid.c
+++ b/fs/9p/fid.c
@@ -154,7 +154,7 @@ static int build_path_from_dentry(struct v9fs_session_info *v9ses,
 	for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
 		n++;
 
-	wnames = kmalloc_array(n, sizeof(char *), GFP_KERNEL);
+	wnames = kmalloc_array(n, sizeof(*wnames), GFP_KERNEL);
 	if (!wnames)
 		goto err_out;
 
-- 
2.34.1

Re: [PATCH] 9p: Add const and unsigned to wnames allocation type

[Dominique Martinet]

Kees Cook wrote on Thu, Sep 17, 2026 at 02:11:59PM -0700:
> From: Kees Cook <kees+treewide@kernel.org>
> 
> In preparation for converting the kmalloc family of allocators to the
> type-aware kmalloc_obj family, we need to make sure that the returned
> type from the allocation matches the type of the variable being
> assigned. (The kmalloc family returns "void *", which can be implicitly
> cast to any pointer type.)
> 
> The assigned type is "const unsigned char **", but the converted
> allocation type would be "char **", which differs in both the const
> qualifier and the signedness of the character type. Take the size from
> the assignment target instead. No change in allocation size results.
> 
> Build tested ARCH=x86_64 allmodconfig with GCC 16.2.0:
> fs/9p/fid.o
> 
> Assisted-by: LLM coccinelle
> Signed-off-by: Kees Cook <kees+treewide@kernel.org>

Ack, will pick up this weekend for 7.4

-- 
Dominique