| Message ID | 1479150736-28392-1-git-send-email-jlayton@redhat.com (mailing list archive) |
|---|---|
| State | Rejected, archived |
| Headers | show |
On Mon, Nov 14, 2016 at 02:12:16PM -0500, Jeff Layton wrote: > We have been seeing errors like this for a while now in the sparse > Fedora package, when doing kernel builds: > > ./include/linux/err.h:53:25: warning: dereference of noderef expression > ./include/linux/err.h:35:16: warning: dereference of noderef expression > > This spews all over the build because this comes from IS_ERR(), which > is called everywhere. Even odder, it turns out that if we build the > package with -fpic turned off, then it works fine. > > With some brute-force debugging, I think I've finally found the cause. > This array is missing the SForced element. When this is added then the > problem goes away. > > As to why this goes away when -fpic is removed, I can only assume that > we get lucky with the memory layout and have a zeroed out region just > beyond the end of the array. > > Fixes: 3829c4d8b097776e6b3472290a9fae08a705ab7a > Cc: Al Viro <viro@ftp.linux.org.uk> > Signed-off-by: Jeff Layton <jlayton@redhat.com> > --- > parse.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/parse.c b/parse.c > index 205e12644a6c..b290ff2636f2 100644 > --- a/parse.c > +++ b/parse.c > @@ -1286,7 +1286,8 @@ static unsigned long storage_modifiers(struct decl_state *ctx) > [SAuto] = MOD_AUTO, > [SExtern] = MOD_EXTERN, > [SStatic] = MOD_STATIC, > - [SRegister] = MOD_REGISTER > + [SRegister] = MOD_REGISTER, > + [SForced] = 0 > }; > return mod[ctx->storage_class] | (ctx->is_inline ? MOD_INLINE : 0) > | (ctx->is_tls ? MOD_TLS : 0); > -- Humm, The array is statically initialized and never modified, your patch shouldn't change anything, and this regardless of the memory layout or compiler options. Luc Van Oostenryck -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Nov 14, 2016 at 12:04 PM, Luc Van Oostenryck <luc.vanoostenryck@gmail.com> wrote: > > The array is statically initialized and never modified, > your patch shouldn't change anything, and this regardless of > the memory layout or compiler options. The problem is the _size_ of the array. Without that initializer for SForced case, it is one entry too small, and you get a random access past the end of the array. The patch is definitely correct. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Nov 14, 2016 at 12:17:47PM -0800, Linus Torvalds wrote: > On Mon, Nov 14, 2016 at 12:04 PM, Luc Van Oostenryck > <luc.vanoostenryck@gmail.com> wrote: > > > > The array is statically initialized and never modified, > > your patch shouldn't change anything, and this regardless of > > the memory layout or compiler options. > > The problem is the _size_ of the array. Without that initializer for > SForced case, it is one entry too small, and you get a random access > past the end of the array. > > The patch is definitely correct. > > Linus > -- Ah yes, indeed. Thanks -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/parse.c b/parse.c index 205e12644a6c..b290ff2636f2 100644 --- a/parse.c +++ b/parse.c @@ -1286,7 +1286,8 @@ static unsigned long storage_modifiers(struct decl_state *ctx) [SAuto] = MOD_AUTO, [SExtern] = MOD_EXTERN, [SStatic] = MOD_STATIC, - [SRegister] = MOD_REGISTER + [SRegister] = MOD_REGISTER, + [SForced] = 0 }; return mod[ctx->storage_class] | (ctx->is_inline ? MOD_INLINE : 0) | (ctx->is_tls ? MOD_TLS : 0);
We have been seeing errors like this for a while now in the sparse Fedora package, when doing kernel builds: ./include/linux/err.h:53:25: warning: dereference of noderef expression ./include/linux/err.h:35:16: warning: dereference of noderef expression This spews all over the build because this comes from IS_ERR(), which is called everywhere. Even odder, it turns out that if we build the package with -fpic turned off, then it works fine. With some brute-force debugging, I think I've finally found the cause. This array is missing the SForced element. When this is added then the problem goes away. As to why this goes away when -fpic is removed, I can only assume that we get lucky with the memory layout and have a zeroed out region just beyond the end of the array. Fixes: 3829c4d8b097776e6b3472290a9fae08a705ab7a Cc: Al Viro <viro@ftp.linux.org.uk> Signed-off-by: Jeff Layton <jlayton@redhat.com> --- parse.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)