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Thu, 07 Aug 2025 00:58:16 -0700 (PDT) From: "Uladzislau Rezki (Sony)" To: linux-mm@kvack.org, Andrew Morton Cc: Vlastimil Babka , Michal Hocko , Baoquan He , LKML , Uladzislau Rezki , Andrey Ryabinin , Alexander Potapenko Subject: [PATCH 5/8] mm/kasan, mm/vmalloc: Respect GFP flags in kasan_populate_vmalloc() Date: Thu, 7 Aug 2025 09:58:07 +0200 Message-Id: <20250807075810.358714-6-urezki@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250807075810.358714-1-urezki@gmail.com> References: <20250807075810.358714-1-urezki@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The function kasan_populate_vmalloc() internally allocates a page using a hardcoded GFP_KERNEL flag. This is not safe in contexts where non-blocking allocation flags are required, such as GFP_ATOMIC or GFP_NOWAIT, for example during atomic vmalloc paths. This patch modifies kasan_populate_vmalloc() and its helpers to accept a gfp_mask argument to use it for a page allocation. It allows the caller to specify the correct allocation context. Also, when non-blocking flags are used, memalloc_noreclaim_save/restore() is used around apply_to_page_range() to suppress potential reclaim behavior that may otherwise violate atomic constraints. Cc: Andrey Ryabinin Cc: Alexander Potapenko Signed-off-by: Uladzislau Rezki (Sony) --- include/linux/kasan.h | 6 +++--- mm/kasan/shadow.c | 22 +++++++++++++++------- mm/vmalloc.c | 4 ++-- 3 files changed, 20 insertions(+), 12 deletions(-) diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 890011071f2b..fe5ce9215821 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -562,7 +562,7 @@ static inline void kasan_init_hw_tags(void) { } #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) =20 void kasan_populate_early_vm_area_shadow(void *start, unsigned long size); -int kasan_populate_vmalloc(unsigned long addr, unsigned long size); +int kasan_populate_vmalloc(unsigned long addr, unsigned long size, gfp_t g= fp_mask); void kasan_release_vmalloc(unsigned long start, unsigned long end, unsigned long free_region_start, unsigned long free_region_end, @@ -574,7 +574,7 @@ static inline void kasan_populate_early_vm_area_shadow(= void *start, unsigned long size) { } static inline int kasan_populate_vmalloc(unsigned long start, - unsigned long size) + unsigned long size, gfp_t gfp_mask) { return 0; } @@ -610,7 +610,7 @@ static __always_inline void kasan_poison_vmalloc(const = void *start, static inline void kasan_populate_early_vm_area_shadow(void *start, unsigned long size) { } static inline int kasan_populate_vmalloc(unsigned long start, - unsigned long size) + unsigned long size, gfp_t gfp_mask) { return 0; } diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c index d2c70cd2afb1..5edfc1f6b53e 100644 --- a/mm/kasan/shadow.c +++ b/mm/kasan/shadow.c @@ -335,13 +335,13 @@ static void ___free_pages_bulk(struct page **pages, i= nt nr_pages) } } =20 -static int ___alloc_pages_bulk(struct page **pages, int nr_pages) +static int ___alloc_pages_bulk(struct page **pages, int nr_pages, gfp_t gf= p_mask) { unsigned long nr_populated, nr_total =3D nr_pages; struct page **page_array =3D pages; =20 while (nr_pages) { - nr_populated =3D alloc_pages_bulk(GFP_KERNEL, nr_pages, pages); + nr_populated =3D alloc_pages_bulk(gfp_mask, nr_pages, pages); if (!nr_populated) { ___free_pages_bulk(page_array, nr_total - nr_pages); return -ENOMEM; @@ -353,25 +353,33 @@ static int ___alloc_pages_bulk(struct page **pages, i= nt nr_pages) return 0; } =20 -static int __kasan_populate_vmalloc(unsigned long start, unsigned long end) +static int __kasan_populate_vmalloc(unsigned long start, unsigned long end= , gfp_t gfp_mask) { unsigned long nr_pages, nr_total =3D PFN_UP(end - start); + bool noblock =3D !gfpflags_allow_blocking(gfp_mask); struct vmalloc_populate_data data; + unsigned int flags; int ret =3D 0; =20 - data.pages =3D (struct page **)__get_free_page(GFP_KERNEL | __GFP_ZERO); + data.pages =3D (struct page **)__get_free_page(gfp_mask | __GFP_ZERO); if (!data.pages) return -ENOMEM; =20 while (nr_total) { nr_pages =3D min(nr_total, PAGE_SIZE / sizeof(data.pages[0])); - ret =3D ___alloc_pages_bulk(data.pages, nr_pages); + ret =3D ___alloc_pages_bulk(data.pages, nr_pages, gfp_mask); if (ret) break; =20 data.start =3D start; + if (noblock) + flags =3D memalloc_noreclaim_save(); + ret =3D apply_to_page_range(&init_mm, start, nr_pages * PAGE_SIZE, kasan_populate_vmalloc_pte, &data); + if (noblock) + memalloc_noreclaim_restore(flags); + ___free_pages_bulk(data.pages, nr_pages); if (ret) break; @@ -385,7 +393,7 @@ static int __kasan_populate_vmalloc(unsigned long start= , unsigned long end) return ret; } =20 -int kasan_populate_vmalloc(unsigned long addr, unsigned long size) +int kasan_populate_vmalloc(unsigned long addr, unsigned long size, gfp_t g= fp_mask) { unsigned long shadow_start, shadow_end; int ret; @@ -414,7 +422,7 @@ int kasan_populate_vmalloc(unsigned long addr, unsigned= long size) shadow_start =3D PAGE_ALIGN_DOWN(shadow_start); shadow_end =3D PAGE_ALIGN(shadow_end); =20 - ret =3D __kasan_populate_vmalloc(shadow_start, shadow_end); + ret =3D __kasan_populate_vmalloc(shadow_start, shadow_end, gfp_mask); if (ret) return ret; =20 diff --git a/mm/vmalloc.c b/mm/vmalloc.c index b0255e0c74b3..7f48a54ec108 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2099,7 +2099,7 @@ static struct vmap_area *alloc_vmap_area(unsigned lon= g size, BUG_ON(va->va_start < vstart); BUG_ON(va->va_end > vend); =20 - ret =3D kasan_populate_vmalloc(addr, size); + ret =3D kasan_populate_vmalloc(addr, size, gfp_mask); if (ret) { free_vmap_area(va); return ERR_PTR(ret); @@ -4835,7 +4835,7 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned l= ong *offsets, =20 /* populate the kasan shadow space */ for (area =3D 0; area < nr_vms; area++) { - if (kasan_populate_vmalloc(vas[area]->va_start, sizes[area])) + if (kasan_populate_vmalloc(vas[area]->va_start, sizes[area], GFP_KERNEL)) goto err_free_shadow; } =20 --=20 2.39.5