kernel.h: fix new warnings for container_of()
PATCH 1/1 kernel.h: fix new warnings for container_of()
I see new warnings with gcc-7.0.1 with the modified container_of():
fs/f2fs/dir.c: In function 'F2FS_I':fs/f2fs/f2fs.h:1122:385: note: found mismatched ssa struct pointer types: 'struct f2fs_inode_info' and 'struct inode'
This seems to happen for all structures that have a zero offset between the member and the container structure, i.e. idential pointers.
Reverting to an intermediate pointer avoids the warning, and using a void pointer instead of the target type should also avoid regressing on the previous patch again.
--- include/linux/kernel.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
include/linux/kernel.h +2 -1
@@ -856,10 +856,11 @@ static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { }* */ #define container_of (ptr, type, member) ({ \ + void *__mptr = (void *)(ptr); \ BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \ !__same_type(*(ptr), void), \ "pointer type mismatch in container_of()"); \ - ((type *)((char *)(ptr) - offsetof(type, member))); }) + ((type *)(__mptr - offsetof(type, member))); })/* Rebuild everything on CONFIG_FTRACE_MCOUNT_RECORD */ #ifdef CONFIG_FTRACE_MCOUNT_RECORD
Signature · 1 line
2.9.0
Quoted 4 lines · Arnd Bergmann
I see new warnings with gcc-7.0.1 with the modified
container_of():
fs/f2fs/dir.c: In function 'F2FS_I':fs/f2fs/f2fs.h:1122:385: note: found mismatched ssa struct pointer types: 'structf2fs_inode_info' and 'struct inode'
This is actually from the randstruct plugin, not native gcc. I'll go update the message reporting to include a "randstruct: " which should make this more obvious.
Quoted 10 lines
This seems to happen for all structures that have a zero offset between the member and the container structure, i.e. idential pointers.
Reverting to an intermediate pointer avoids the warning, and using a void pointer instead of the target type should also avoid regressing on the previous patch again.
Fixes mmotm ("kernel.h: handle pointers to arrays better in container_of()")Signed-off-by Arnd Bergmann <[email protected]>
Thanks!
I'll take this into the kspp tree so all the fixes are in the same place.
-Kees
Signature · 2 lines
Kees Cook Pixel Security
Quoted 18 lines · Kees Cook
Quoted 4 lines · Arnd Bergmann
I see new warnings with gcc-7.0.1 with the modified
container_of():
fs/f2fs/dir.c: In function 'F2FS_I':fs/f2fs/f2fs.h:1122:385: note: found mismatched ssa struct pointer types: 'structf2fs_inode_info' and 'struct inode'This is actually from the randstruct plugin, not native gcc. I'll go update the message reporting to include a "randstruct: " which should make this more obvious.
Quoted 8 lines
This seems to happen for all structures that have a zero offset between the member and the container structure, i.e. idential pointers.
Reverting to an intermediate pointer avoids the warning, and using a void pointer instead of the target type should also avoid regressing on the previous patch again.
Quoted 6 lines
Quoted 2 lines
Fixes mmotm ("kernel.h: handle pointers to arrays better in container_of()")Signed-off-by Arnd Bergmann <[email protected]>Thanks!
I'll take this into the kspp tree so all the fixes are in the same place.
Oh, nevermind, I see the Fixes is for what's already in -mm. :) And I see akpm picked this up already. Sorry for the noise!
-Kees
Signature · 2 lines
Kees Cook Pixel Security
Quoted 4 lines · Arnd Bergmann
I see new warnings with gcc-7.0.1 with the modified
container_of():
fs/f2fs/dir.c: In function 'F2FS_I':fs/f2fs/f2fs.h:1122:385: note: found mismatched ssa struct pointer types: 'structf2fs_inode_info' and 'struct inode'
Is that actually a warning, or just informational? In any case, it seems like a good idea to avoid it.
Quoted 23 lines
This seems to happen for all structures that have a zero offset between the member and the container structure, i.e. idential pointers.
Reverting to an intermediate pointer avoids the warning, and using a void pointer instead of the target type should also avoid regressing on the previous patch again.
Fixes mmotm ("kernel.h: handle pointers to arrays better in container_of()")Signed-off-by Arnd Bergmann <[email protected]>--- include/linux/kernel.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)include/linux/kernel.h +0
-0@@ -856,10 +856,11 @@ static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { }* */
include/linux/kernel.h static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { } · line 866
Quoted 10 lines
include/linux/kernel.h +2
-1#define container_of (ptr, type, member) ({ \ + void *__mptr = (void *)(ptr); \ BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \ !__same_type(*(ptr), void), \ "pointer type mismatch in container_of()"); \ - ((type *)((char *)(ptr) - offsetof(type, member))); }) + ((type *)(__mptr - offsetof(type, member))); })/* Rebuild everything on CONFIG_FTRACE_MCOUNT_RECORD */ #ifdef CONFIG_FTRACE_MCOUNT_RECORD
Signature · 2 lines
-=( Ian Abbott @ MEV Ltd. E-mail: <[email protected]> )=- -=( Web: http://www.mev.co.uk/ )=-
Quoted 11 lines · Ian Abbott
Quoted 6 lines · Arnd Bergmann
I see new warnings with gcc-7.0.1 with the modified
container_of():
fs/f2fs/dir.c: In function 'F2FS_I':fs/f2fs/f2fs.h:1122:385: note: found mismatched ssa struct pointer types:
'structf2fs_inode_info' and 'struct inode'Is that actually a warning, or just informational? In any case, it seems like a good idea to avoid it.
It's informational, not a warning. I couldn't actually figure out what the message is trying to tell me here. Maybe the message could also be improved?
Arnd