| Message ID | 20220612213227.3881769-4-willy@infradead.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Fixes for usercopy | expand |
> If 'n' is so large that it's negative, we might wrap around and mistakenly > think that the copy is OK when it's not. Such a copy would probably > crash, but just doing the arithmetic in a more simple way lets us detect > and refuse this case. > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > --- > mm/usercopy.c | 19 +++++++++---------- > 1 file changed, 9 insertions(+), 10 deletions(-) > > diff --git a/mm/usercopy.c b/mm/usercopy.c > index 31deee7dd2f5..ff16083cf1c8 100644 > --- a/mm/usercopy.c > +++ b/mm/usercopy.c > @@ -162,20 +162,18 @@ static inline void check_heap_object(const void *ptr, unsigned long n, > bool to_user) > { > uintptr_t addr = (uintptr_t)ptr; > + unsigned long offset; > struct folio *folio; > > if (is_kmap_addr(ptr)) { > - unsigned long page_end = addr | (PAGE_SIZE - 1); > - > - if (addr + n - 1 > page_end) > - usercopy_abort("kmap", NULL, to_user, > - offset_in_page(ptr), n); > + offset = offset_in_page(ptr); > + if (n > PAGE_SIZE - offset) > + usercopy_abort("kmap", NULL, to_user, offset, n); > return; > } > > if (is_vmalloc_addr(ptr)) { > struct vmap_area *area = find_vmap_area(addr); > - unsigned long offset; > > if (!area) { > usercopy_abort("vmalloc", "no area", to_user, 0, n); > @@ -184,9 +182,10 @@ static inline void check_heap_object(const void *ptr, unsigned long n, > > /* XXX: We should also abort for free vmap_areas */ > > - offset = addr - area->va_start; > - if (addr + n > area->va_end) > + if (n > area->va_end - addr) { > + offset = addr - area->va_start; > usercopy_abort("vmalloc", NULL, to_user, offset, n); > + } > return; > } > > @@ -199,8 +198,8 @@ static inline void check_heap_object(const void *ptr, unsigned long n, > /* Check slab allocator for flags and size. */ > __check_heap_object(ptr, n, folio_slab(folio), to_user); > } else if (folio_test_large(folio)) { > - unsigned long offset = ptr - folio_address(folio); > - if (offset + n > folio_size(folio)) > + offset = ptr - folio_address(folio); > + if (n > folio_size(folio) - offset) > usercopy_abort("page alloc", NULL, to_user, offset, n); > } > } > -- > 2.35.1 > Looks good to me: Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com> -- Uladzislau Rezki
diff --git a/mm/usercopy.c b/mm/usercopy.c index 31deee7dd2f5..ff16083cf1c8 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -162,20 +162,18 @@ static inline void check_heap_object(const void *ptr, unsigned long n, bool to_user) { uintptr_t addr = (uintptr_t)ptr; + unsigned long offset; struct folio *folio; if (is_kmap_addr(ptr)) { - unsigned long page_end = addr | (PAGE_SIZE - 1); - - if (addr + n - 1 > page_end) - usercopy_abort("kmap", NULL, to_user, - offset_in_page(ptr), n); + offset = offset_in_page(ptr); + if (n > PAGE_SIZE - offset) + usercopy_abort("kmap", NULL, to_user, offset, n); return; } if (is_vmalloc_addr(ptr)) { struct vmap_area *area = find_vmap_area(addr); - unsigned long offset; if (!area) { usercopy_abort("vmalloc", "no area", to_user, 0, n); @@ -184,9 +182,10 @@ static inline void check_heap_object(const void *ptr, unsigned long n, /* XXX: We should also abort for free vmap_areas */ - offset = addr - area->va_start; - if (addr + n > area->va_end) + if (n > area->va_end - addr) { + offset = addr - area->va_start; usercopy_abort("vmalloc", NULL, to_user, offset, n); + } return; } @@ -199,8 +198,8 @@ static inline void check_heap_object(const void *ptr, unsigned long n, /* Check slab allocator for flags and size. */ __check_heap_object(ptr, n, folio_slab(folio), to_user); } else if (folio_test_large(folio)) { - unsigned long offset = ptr - folio_address(folio); - if (offset + n > folio_size(folio)) + offset = ptr - folio_address(folio); + if (n > folio_size(folio) - offset) usercopy_abort("page alloc", NULL, to_user, offset, n); } }
If 'n' is so large that it's negative, we might wrap around and mistakenly think that the copy is OK when it's not. Such a copy would probably crash, but just doing the arithmetic in a more simple way lets us detect and refuse this case. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> --- mm/usercopy.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-)