Re: [PATCH v2 3/3] mm/usercopy: Detect compound page overruns
From: Kees Cook <hidden>
Date: 2021-10-06 22:07:43
On Wed, Oct 06, 2021 at 03:08:46PM +0100, Matthew Wilcox wrote:
On Wed, Oct 06, 2021 at 01:42:26PM +0100, Matthew Wilcox (Oracle) wrote:quoted
Move the compound page overrun detection out of CONFIG_HARDENED_USERCOPY_PAGESPAN so it's enabled for more people. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Acked-by: Kees Cook <redacted> --- mm/usercopy.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)diff --git a/mm/usercopy.c b/mm/usercopy.c index 63476e1506e0..b825c4344917 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c@@ -194,11 +194,6 @@ static inline void check_page_span(const void *ptr, unsigned long n, ((unsigned long)end & (unsigned long)PAGE_MASK))) return; - /* Allow if fully inside the same compound (__GFP_COMP) page. */ - endpage = virt_to_head_page(end); - if (likely(endpage == page)) - return; - /* * Reject if range is entirely either Reserved (i.e. special or * device memory), or CMA. Otherwise, reject since the object spansNeeds an extra hunk to avoid a warning with that config:
Ah yeah, good catch.
quoted hunk ↗ jump to hunk
@@ -163,7 +163,6 @@ static inline void check_page_span(const void *ptr, unsigned long n, { #ifdef CONFIG_HARDENED_USERCOPY_PAGESPAN const void *end = ptr + n - 1; - struct page *endpage; bool is_reserved, is_cma; /*I'll wait a few days and send a v3.
When you send v3, can you CC linux-hardening@vger.kernel.org too? Thanks for poking at this! -Kees -- Kees Cook