Commit c51a4f11 authored by Zi Yan's avatar Zi Yan Committed by Andrew Morton
Browse files

mm: use clear_user_(high)page() for arch with special user folio handling 

Some architectures have special handling after clearing user folios:
architectures, which set cpu_dcache_is_aliasing() to true, require
flushing dcache; arc, which sets cpu_icache_is_aliasing() to true, changes
folio->flags to make icache coherent to dcache.  So __GFP_ZERO using only
clear_page() is not enough to zero user folios and clear_user_(high)page()
must be used.  Otherwise, user data will be corrupted.

Fix it by always clearing user folios with clear_user_(high)page() when
cpu_dcache_is_aliasing() is true or cpu_icache_is_aliasing() is true. 
Rename alloc_zeroed() to user_alloc_needs_zeroing() and invert the logic
to clarify its intend.

Link: https://lkml.kernel.org/r/20241209182326.2955963-2-ziy@nvidia.com


Fixes: 5708d96d ("mm: avoid zeroing user movable page twice with init_on_alloc=1")
Signed-off-by: default avatarZi Yan <ziy@nvidia.com>
Reported-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Closes: https://lore.kernel.org/linux-mm/CAMuHMdV1hRp_NtR5YnJo=HsfgKQeH91J537Gh4gKk3PFZhSkbA@mail.gmail.com/


Tested-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Alexander Potapenko <glider@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vineet Gupta <vgupta@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 5c0541e1

include/linux/highmem.h

+7 −1
Original line number Diff line number Diff line
@@ -224,7 +224,13 @@ static inline 
struct folio *vma_alloc_zeroed_movable_folio(struct vm_area_struct *vma,

				   unsigned long vaddr)

{

	return vma_alloc_folio(GFP_HIGHUSER_MOVABLE | __GFP_ZERO, 0, vma, vaddr);

	struct folio *folio;



	folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vaddr);

	if (folio && user_alloc_needs_zeroing())

		clear_user_highpage(&folio->page, vaddr);



	return folio;

}

#endif

include/linux/mm.h

+18 −0
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ 
#include <linux/kasan.h>

#include <linux/memremap.h>

#include <linux/slab.h>

#include <linux/cacheinfo.h>



struct mempolicy;

struct anon_vma;
@@ -4184,6 +4185,23 @@ static inline int do_mseal(unsigned long start, size_t len_in, unsigned long fla 
}

#endif



/*

 * user_alloc_needs_zeroing checks if a user folio from page allocator needs to

 * be zeroed or not.

 */

static inline bool user_alloc_needs_zeroing(void)

{

	/*

	 * for user folios, arch with cache aliasing requires cache flush and

	 * arc changes folio->flags to make icache coherent with dcache, so

	 * always return false to make caller use

	 * clear_user_page()/clear_user_highpage().

	 */

	return cpu_dcache_is_aliasing() || cpu_icache_is_aliasing() ||

	       !static_branch_maybe(CONFIG_INIT_ON_ALLOC_DEFAULT_ON,

				   &init_on_alloc);

}



int arch_get_shadow_stack_status(struct task_struct *t, unsigned long __user *status);

int arch_set_shadow_stack_status(struct task_struct *t, unsigned long status);

int arch_lock_shadow_stack_status(struct task_struct *t, unsigned long status);

mm/huge_memory.c

+5 −4
Original line number Diff line number Diff line
@@ -1176,11 +1176,12 @@ static struct folio *vma_alloc_anon_folio_pmd(struct vm_area_struct *vma, 
	folio_throttle_swaprate(folio, gfp);



       /*

	* When a folio is not zeroed during allocation (__GFP_ZERO not used),

	* folio_zero_user() is used to make sure that the page corresponding

	* to the faulting address will be hot in the cache after zeroing.

	* When a folio is not zeroed during allocation (__GFP_ZERO not used)

	* or user folios require special handling, folio_zero_user() is used to

	* make sure that the page corresponding to the faulting address will be

	* hot in the cache after zeroing.

	*/

	if (!alloc_zeroed())

	if (user_alloc_needs_zeroing())

		folio_zero_user(folio, addr);

	/*

	 * The memory barrier inside __folio_mark_uptodate makes sure that

mm/internal.h

+0 −6
Original line number Diff line number Diff line
@@ -1285,12 +1285,6 @@ void touch_pud(struct vm_area_struct *vma, unsigned long addr, 
void touch_pmd(struct vm_area_struct *vma, unsigned long addr,

	       pmd_t *pmd, bool write);



static inline bool alloc_zeroed(void)

{

	return static_branch_maybe(CONFIG_INIT_ON_ALLOC_DEFAULT_ON,

			&init_on_alloc);

}



/*

 * Parses a string with mem suffixes into its order. Useful to parse kernel

 * parameters.

mm/memory.c

+5 −5
Original line number Diff line number Diff line
@@ -4733,12 +4733,12 @@ static struct folio *alloc_anon_folio(struct vm_fault *vmf) 
			folio_throttle_swaprate(folio, gfp);

			/*

			 * When a folio is not zeroed during allocation

			 * (__GFP_ZERO not used), folio_zero_user() is used

			 * to make sure that the page corresponding to the

			 * faulting address will be hot in the cache after

			 * zeroing.

			 * (__GFP_ZERO not used) or user folios require special

			 * handling, folio_zero_user() is used to make sure

			 * that the page corresponding to the faulting address

			 * will be hot in the cache after zeroing.

			 */

			if (!alloc_zeroed())

			if (user_alloc_needs_zeroing())

				folio_zero_user(folio, vmf->address);

			return folio;

		}