2023-09-22 20:43:04

by Mike Tipton

Subject: [PATCH] debugfs: Fix __rcu type comparison warning

Sparse reports the following:

fs/debugfs/file.c:942:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
fs/debugfs/file.c:942:9: sparse: char [noderef] __rcu *
fs/debugfs/file.c:942:9: sparse: char *

rcu_assign_pointer() expects that it's assigning to pointers annotated
with __rcu. We can't annotate the generic struct file::private_data, so
cast it instead.

Fixes: 86b5488121db ("debugfs: Add write support to debugfs_create_str()")
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Signed-off-by: Mike Tipton <[email protected]>
---
fs/debugfs/file.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 87b3753aa4b1..c45e8c2d62e1 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -939,7 +939,7 @@ static ssize_t debugfs_write_file_str(struct file *file, const char __user *user
new[pos + count] = '\0';
strim(new);

- rcu_assign_pointer(*(char **)file->private_data, new);
+ rcu_assign_pointer(*(char __rcu **)file->private_data, new);
synchronize_rcu();
kfree(old);

--
2.17.1

2023-10-09 21:46:10

by Georgi Djakov

Subject: Re: [PATCH] debugfs: Fix __rcu type comparison warning

On 22.09.23 16:45, Mike Tipton wrote:
> Sparse reports the following:
>
> fs/debugfs/file.c:942:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
> fs/debugfs/file.c:942:9: sparse: char [noderef] __rcu *
> fs/debugfs/file.c:942:9: sparse: char *
>
> rcu_assign_pointer() expects that it's assigning to pointers annotated
> with __rcu. We can't annotate the generic struct file::private_data, so
> cast it instead.
>
> Fixes: 86b5488121db ("debugfs: Add write support to debugfs_create_str()")
> Reported-by: kernel test robot <[email protected]>
> Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
> Signed-off-by: Mike Tipton <[email protected]>

Reviewed-by: Georgi Djakov <[email protected]>

> ---
> fs/debugfs/file.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
> index 87b3753aa4b1..c45e8c2d62e1 100644
> --- a/fs/debugfs/file.c
> +++ b/fs/debugfs/file.c
> @@ -939,7 +939,7 @@ static ssize_t debugfs_write_file_str(struct file *file, const char __user *user
> new[pos + count] = '\0';
> strim(new);
>
> - rcu_assign_pointer(*(char **)file->private_data, new);
> + rcu_assign_pointer(*(char __rcu **)file->private_data, new);
> synchronize_rcu();
> kfree(old);
>