| Message ID | 20241207171631.2853336-2-ziy@nvidia.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v4,1/2] Introduce cpu_icache_is_aliasing() across all architectures | expand |
On 12/7/24 18:16, Zi Yan wrote: > 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 alloc_need_zeroing() and invert the logic to > clarify its intend. user_alloc_needs_zeroing() would be perhaps more descriptive? > Fixes: 5708d96da20b ("mm: avoid zeroing user movable page twice with init_on_alloc=1") > Reported-by: Geert Uytterhoeven <geert+renesas@glider.be> > Closes: https://lore.kernel.org/linux-mm/CAMuHMdV1hRp_NtR5YnJo=HsfgKQeH91J537Gh4gKk3PFZhSkbA@mail.gmail.com/ > Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> > Signed-off-by: Zi Yan <ziy@nvidia.com> Acked-by: Vlastimil Babka <vbabka@suse.cz>
On 9 Dec 2024, at 13:12, Vlastimil Babka wrote: > On 12/7/24 18:16, Zi Yan wrote: >> 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 alloc_need_zeroing() and invert the logic to >> clarify its intend. > > user_alloc_needs_zeroing() would be perhaps more descriptive? Sounds good. Let me send v5. > >> Fixes: 5708d96da20b ("mm: avoid zeroing user movable page twice with init_on_alloc=1") >> Reported-by: Geert Uytterhoeven <geert+renesas@glider.be> >> Closes: https://lore.kernel.org/linux-mm/CAMuHMdV1hRp_NtR5YnJo=HsfgKQeH91J537Gh4gKk3PFZhSkbA@mail.gmail.com/ >> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> >> Signed-off-by: Zi Yan <ziy@nvidia.com> > > Acked-by: Vlastimil Babka <vbabka@suse.cz> Thanks. Best Regards, Yan, Zi
diff --git a/include/linux/highmem.h b/include/linux/highmem.h index 6e452bd8e7e3..d9beb8371daa 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -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 && alloc_need_zeroing()) + clear_user_highpage(&folio->page, vaddr); + + return folio; } #endif diff --git a/include/linux/mm.h b/include/linux/mm.h index c39c4945946c..9330b60b926f 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -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; @@ -4175,6 +4176,23 @@ static inline int do_mseal(unsigned long start, size_t len_in, unsigned long fla } #endif +/* + * alloc_need_zeroing checks if a user folio from page allocator needs to be + * zeroed or not. + */ +static inline bool alloc_need_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); diff --git a/mm/huge_memory.c b/mm/huge_memory.c index ee335d96fc39..107130a5413a 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -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 (alloc_need_zeroing()) folio_zero_user(folio, addr); /* * The memory barrier inside __folio_mark_uptodate makes sure that diff --git a/mm/internal.h b/mm/internal.h index cb8d8e8e3ffa..3bd08bafad04 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -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. diff --git a/mm/memory.c b/mm/memory.c index 75c2dfd04f72..cf1611791856 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -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 (alloc_need_zeroing()) folio_zero_user(folio, vmf->address); return folio; }
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 alloc_need_zeroing() and invert the logic to clarify its intend. Fixes: 5708d96da20b ("mm: avoid zeroing user movable page twice with init_on_alloc=1") Reported-by: Geert Uytterhoeven <geert+renesas@glider.be> Closes: https://lore.kernel.org/linux-mm/CAMuHMdV1hRp_NtR5YnJo=HsfgKQeH91J537Gh4gKk3PFZhSkbA@mail.gmail.com/ Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by: Zi Yan <ziy@nvidia.com> --- include/linux/highmem.h | 8 +++++++- include/linux/mm.h | 18 ++++++++++++++++++ mm/huge_memory.c | 9 +++++---- mm/internal.h | 6 ------ mm/memory.c | 10 +++++----- 5 files changed, 35 insertions(+), 16 deletions(-)