| Message ID | 20170620200940.90557-1-arnd@arndb.de |
|---|---|
| State | New |
| Headers | show |
On Tue, Jun 20, 2017 at 1:09 PM, Arnd Bergmann <arnd@arndb.de> wrote: > 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 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. > 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 <arnd@arndb.de> Thanks! I'll take this into the kspp tree so all the fixes are in the same place. -Kees -- Kees Cook Pixel Security
On Tue, Jun 20, 2017 at 3:43 PM, Kees Cook <keescook@chromium.org> wrote: > On Tue, Jun 20, 2017 at 1:09 PM, Arnd Bergmann <arnd@arndb.de> wrote: >> 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 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. > >> 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 <arnd@arndb.de> > > 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 -- Kees Cook Pixel Security
On 20/06/17 21:09, Arnd Bergmann wrote: > 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' Is that actually a warning, or just informational? In any case, it seems like a good idea to avoid it. > > 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 <arnd@arndb.de> > --- > include/linux/kernel.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > index d043adadcf33..bd6d96cf80b1 100644 > --- a/include/linux/kernel.h > +++ b/include/linux/kernel.h > @@ -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 > Acked-by: Ian Abbott <abbotti@mev.co.uk> -- -=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@mev.co.uk> )=- -=( Web: http://www.mev.co.uk/ )=-
On Wed, Jun 21, 2017 at 11:25 AM, Ian Abbott <abbotti@mev.co.uk> wrote: > On 20/06/17 21:09, Arnd Bergmann wrote: >> >> 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' > > > 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
diff --git a/include/linux/kernel.h b/include/linux/kernel.h index d043adadcf33..bd6d96cf80b1 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -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
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. Fixes: mmotm ("kernel.h: handle pointers to arrays better in container_of()") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- include/linux/kernel.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) -- 2.9.0