| Message ID | 20241018151112.3533820-1-arnd@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: export copy_to_kernel_nofault | expand |
On 18.10.24 17:11, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > This symbol is now used on the kasan test module, so it needs to be > exported. > > ERROR: modpost: "copy_to_kernel_nofault" [mm/kasan/kasan_test.ko] undefined! > > Fixes: 44749130ffb4 ("kasan: migrate copy_user_test to kunit") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > mm/maccess.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/maccess.c b/mm/maccess.c > index 3ca55ec63a6a..8f0906180a94 100644 > --- a/mm/maccess.c > +++ b/mm/maccess.c > @@ -82,6 +82,7 @@ long copy_to_kernel_nofault(void *dst, const void *src, size_t size) > pagefault_enable(); > return -EFAULT; > } > +EXPORT_SYMBOL_GPL(copy_to_kernel_nofault); > > long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count) > { Acked-by: David Hildenbrand <david@redhat.com>
On Fri, Oct 18, 2024 at 5:11 PM Arnd Bergmann <arnd@kernel.org> wrote: > > From: Arnd Bergmann <arnd@arndb.de> > > This symbol is now used on the kasan test module, so it needs to be > exported. > > ERROR: modpost: "copy_to_kernel_nofault" [mm/kasan/kasan_test.ko] undefined! > > Fixes: 44749130ffb4 ("kasan: migrate copy_user_test to kunit") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > mm/maccess.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/maccess.c b/mm/maccess.c > index 3ca55ec63a6a..8f0906180a94 100644 > --- a/mm/maccess.c > +++ b/mm/maccess.c > @@ -82,6 +82,7 @@ long copy_to_kernel_nofault(void *dst, const void *src, size_t size) > pagefault_enable(); > return -EFAULT; > } > +EXPORT_SYMBOL_GPL(copy_to_kernel_nofault); > > long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count) > { > -- > 2.39.5 > Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com> Thank you!
On Fri, Oct 18, 2024 at 03:11:09PM +0000, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > This symbol is now used on the kasan test module, so it needs to be > exported. > > ERROR: modpost: "copy_to_kernel_nofault" [mm/kasan/kasan_test.ko] undefined! Meh, it would be great not to export internal helpers just because someone wants to test them. Please just mark that test built-in only instead.
On Wed, 23 Oct 2024 at 08:53, Christoph Hellwig <hch@infradead.org> wrote: > > On Fri, Oct 18, 2024 at 03:11:09PM +0000, Arnd Bergmann wrote: > > From: Arnd Bergmann <arnd@arndb.de> > > > > This symbol is now used on the kasan test module, so it needs to be > > exported. > > > > ERROR: modpost: "copy_to_kernel_nofault" [mm/kasan/kasan_test.ko] undefined! > > Meh, it would be great not to export internal helpers just because > someone wants to test them. Please just mark that test built-in only > instead. We have EXPORT_SYMBOL_IF_KUNIT. See include/kunit/visibility.h - that's more appropriate, and also adjust kasan_test.c to do MODULE_IMPORT_NS(EXPORTED_FOR_KUNIT_TESTING).
On Wed, Oct 23, 2024 at 08:57:02AM +0200, Marco Elver wrote: > On Wed, 23 Oct 2024 at 08:53, Christoph Hellwig <hch@infradead.org> wrote: > > > > On Fri, Oct 18, 2024 at 03:11:09PM +0000, Arnd Bergmann wrote: > > > From: Arnd Bergmann <arnd@arndb.de> > > > > > > This symbol is now used on the kasan test module, so it needs to be > > > exported. > > > > > > ERROR: modpost: "copy_to_kernel_nofault" [mm/kasan/kasan_test.ko] undefined! > > > > Meh, it would be great not to export internal helpers just because > > someone wants to test them. Please just mark that test built-in only > > instead. > > We have EXPORT_SYMBOL_IF_KUNIT. See include/kunit/visibility.h - > that's more appropriate, and also adjust kasan_test.c to do > MODULE_IMPORT_NS(EXPORTED_FOR_KUNIT_TESTING). Thats a little better, but at least in this case I still think it is a very bad idea. copy_to_kernel_nofault is a perfect vector for exploit code to probe writing to kernel address without causing faults so it really should never ever be exported.
On Wed, 23 Oct 2024 at 08:59, Christoph Hellwig <hch@infradead.org> wrote: > > On Wed, Oct 23, 2024 at 08:57:02AM +0200, Marco Elver wrote: > > On Wed, 23 Oct 2024 at 08:53, Christoph Hellwig <hch@infradead.org> wrote: > > > > > > On Fri, Oct 18, 2024 at 03:11:09PM +0000, Arnd Bergmann wrote: > > > > From: Arnd Bergmann <arnd@arndb.de> > > > > > > > > This symbol is now used on the kasan test module, so it needs to be > > > > exported. > > > > > > > > ERROR: modpost: "copy_to_kernel_nofault" [mm/kasan/kasan_test.ko] undefined! > > > > > > Meh, it would be great not to export internal helpers just because > > > someone wants to test them. Please just mark that test built-in only > > > instead. > > > > We have EXPORT_SYMBOL_IF_KUNIT. See include/kunit/visibility.h - > > that's more appropriate, and also adjust kasan_test.c to do > > MODULE_IMPORT_NS(EXPORTED_FOR_KUNIT_TESTING). > > Thats a little better, but at least in this case I still think it is > a very bad idea. copy_to_kernel_nofault is a perfect vector for > exploit code to probe writing to kernel address without causing faults > so it really should never ever be exported. Another alternative is to just #ifndef MODULE the offending test case, so it's only available if built-in. No need to just make the whole test built-in only. I know there are users of this particular test that rely on it being a module.
On Wed, Oct 23, 2024 at 09:02:23AM +0200, Marco Elver wrote: > Another alternative is to just #ifndef MODULE the offending test case, > so it's only available if built-in. No need to just make the whole > test built-in only. I know there are users of this particular test > that rely on it being a module. That sounds good to me.
On Wed, 23 Oct 2024 00:05:36 -0700 Christoph Hellwig <hch@infradead.org> wrote: > On Wed, Oct 23, 2024 at 09:02:23AM +0200, Marco Elver wrote: > > Another alternative is to just #ifndef MODULE the offending test case, > > so it's only available if built-in. No need to just make the whole > > test built-in only. I know there are users of this particular test > > that rely on it being a module. > > That sounds good to me. We still don't have patch which does this, so this series is stalled. Sabyrzhan, could you please consider this?
diff --git a/mm/maccess.c b/mm/maccess.c index 3ca55ec63a6a..8f0906180a94 100644 --- a/mm/maccess.c +++ b/mm/maccess.c @@ -82,6 +82,7 @@ long copy_to_kernel_nofault(void *dst, const void *src, size_t size) pagefault_enable(); return -EFAULT; } +EXPORT_SYMBOL_GPL(copy_to_kernel_nofault); long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count) {