2023-10-18 18:11:08

by Nathan Chancellor

Subject: [PATCH] eventfs: Use ERR_CAST() in eventfs_create_events_dir()

When building with clang and CONFIG_RANDSTRUCT_FULL=y, there is an error
due to a cast in eventfs_create_events_dir():

fs/tracefs/event_inode.c:734:10: error: casting from randomized structure pointer type 'struct dentry *' to 'struct eventfs_inode *'
734 | return (struct eventfs_inode *)dentry;
| ^
1 error generated.

Use the ERR_CAST() function to resolve the error, as it was designed for
this exact situation (casting an error pointer to another type).

Closes: https://github.com/ClangBuiltLinux/linux/issues/1947
Fixes: 5790b1fb3d67 ("eventfs: Remove eventfs_file and just use eventfs_inode")
Signed-off-by: Nathan Chancellor <[email protected]>
---
fs/tracefs/event_inode.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 1ccd100bc565..9f19b6608954 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -731,7 +731,7 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
return NULL;

if (IS_ERR(dentry))
- return (struct eventfs_inode *)dentry;
+ return ERR_CAST(dentry);

ei = kzalloc(sizeof(*ei), GFP_KERNEL);
if (!ei)

---
base-commit: 5ddd8baa4857709b4e5d84b376d735152851955b
change-id: 20231018-ftrace-fix-clang-randstruct-0cb6899523ac

Best regards,
--
Nathan Chancellor <[email protected]>

2023-10-18 18:14:38

by Kees Cook

Subject: Re: [PATCH] eventfs: Use ERR_CAST() in eventfs_create_events_dir()

On Wed, Oct 18, 2023 at 11:10:31AM -0700, Nathan Chancellor wrote:
> When building with clang and CONFIG_RANDSTRUCT_FULL=y, there is an error
> due to a cast in eventfs_create_events_dir():
>
> fs/tracefs/event_inode.c:734:10: error: casting from randomized structure pointer type 'struct dentry *' to 'struct eventfs_inode *'
> 734 | return (struct eventfs_inode *)dentry;
> | ^
> 1 error generated.
>
> Use the ERR_CAST() function to resolve the error, as it was designed for
> this exact situation (casting an error pointer to another type).
>
> Closes: https://github.com/ClangBuiltLinux/linux/issues/1947
> Fixes: 5790b1fb3d67 ("eventfs: Remove eventfs_file and just use eventfs_inode")
> Signed-off-by: Nathan Chancellor <[email protected]>

Yes, please. That's the correct method to do such casts. Thanks!

Reviewed-by: Kees Cook <[email protected]>

--
Kees Cook