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kasan: remove PG_skip_kasan_poison flag
Code inspection reveals that PG_skip_kasan_poison is redundant with kasantag, because the former is intended to be set iff the latter is the match-all tag. It can also be observed that it's basically pointless to poison pages which have kasantag=0, because any pages with this tag would have been pointed to by pointers with match-all tags, so poisoning the pages would have little to no effect in terms of bug detection. Therefore, change the condition in should_skip_kasan_poison() to check kasantag instead, and remove PG_skip_kasan_poison and associated flags. Link: https://lkml.kernel.org/r/20230310042914.3805818-3-pcc@google.com Link: https://linux-review.googlesource.com/id/I57f825f2eaeaf7e8389d6cf4597c8a5821359838 Signed-off-by: Peter Collingbourne <pcc@google.com> Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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@ -47,16 +47,14 @@ typedef unsigned int __bitwise gfp_t;
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#define ___GFP_ACCOUNT 0x400000u
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#define ___GFP_ZEROTAGS 0x800000u
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#ifdef CONFIG_KASAN_HW_TAGS
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#define ___GFP_SKIP_ZERO 0x1000000u
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#define ___GFP_SKIP_KASAN_UNPOISON 0x2000000u
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#define ___GFP_SKIP_KASAN_POISON 0x4000000u
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#define ___GFP_SKIP_ZERO 0x1000000u
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#define ___GFP_SKIP_KASAN 0x2000000u
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#else
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#define ___GFP_SKIP_ZERO 0
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#define ___GFP_SKIP_KASAN_UNPOISON 0
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#define ___GFP_SKIP_KASAN_POISON 0
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#define ___GFP_SKIP_ZERO 0
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#define ___GFP_SKIP_KASAN 0
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#endif
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#ifdef CONFIG_LOCKDEP
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#define ___GFP_NOLOCKDEP 0x8000000u
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#define ___GFP_NOLOCKDEP 0x4000000u
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#else
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#define ___GFP_NOLOCKDEP 0
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#endif
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@ -234,25 +232,24 @@ typedef unsigned int __bitwise gfp_t;
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* memory tags at the same time as zeroing memory has minimal additional
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* performace impact.
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*
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* %__GFP_SKIP_KASAN_UNPOISON makes KASAN skip unpoisoning on page allocation.
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* Only effective in HW_TAGS mode.
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*
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* %__GFP_SKIP_KASAN_POISON makes KASAN skip poisoning on page deallocation.
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* Typically, used for userspace pages. Only effective in HW_TAGS mode.
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* %__GFP_SKIP_KASAN makes KASAN skip unpoisoning on page allocation.
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* Used for userspace and vmalloc pages; the latter are unpoisoned by
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* kasan_unpoison_vmalloc instead. For userspace pages, results in
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* poisoning being skipped as well, see should_skip_kasan_poison for
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* details. Only effective in HW_TAGS mode.
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*/
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#define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN)
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#define __GFP_COMP ((__force gfp_t)___GFP_COMP)
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#define __GFP_ZERO ((__force gfp_t)___GFP_ZERO)
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#define __GFP_ZEROTAGS ((__force gfp_t)___GFP_ZEROTAGS)
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#define __GFP_SKIP_ZERO ((__force gfp_t)___GFP_SKIP_ZERO)
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#define __GFP_SKIP_KASAN_UNPOISON ((__force gfp_t)___GFP_SKIP_KASAN_UNPOISON)
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#define __GFP_SKIP_KASAN_POISON ((__force gfp_t)___GFP_SKIP_KASAN_POISON)
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#define __GFP_SKIP_KASAN ((__force gfp_t)___GFP_SKIP_KASAN)
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/* Disable lockdep for GFP context tracking */
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#define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP)
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/* Room for N __GFP_FOO bits */
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#define __GFP_BITS_SHIFT (27 + IS_ENABLED(CONFIG_LOCKDEP))
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#define __GFP_BITS_SHIFT (26 + IS_ENABLED(CONFIG_LOCKDEP))
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#define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
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/**
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@ -335,8 +332,7 @@ typedef unsigned int __bitwise gfp_t;
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#define GFP_DMA __GFP_DMA
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#define GFP_DMA32 __GFP_DMA32
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#define GFP_HIGHUSER (GFP_USER | __GFP_HIGHMEM)
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#define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE | \
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__GFP_SKIP_KASAN_POISON | __GFP_SKIP_KASAN_UNPOISON)
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#define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE | __GFP_SKIP_KASAN)
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#define GFP_TRANSHUGE_LIGHT ((GFP_HIGHUSER_MOVABLE | __GFP_COMP | \
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__GFP_NOMEMALLOC | __GFP_NOWARN) & ~__GFP_RECLAIM)
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#define GFP_TRANSHUGE (GFP_TRANSHUGE_LIGHT | __GFP_DIRECT_RECLAIM)
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@ -135,9 +135,6 @@ enum pageflags {
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#ifdef CONFIG_ARCH_USES_PG_ARCH_X
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PG_arch_2,
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PG_arch_3,
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#endif
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#ifdef CONFIG_KASAN_HW_TAGS
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PG_skip_kasan_poison,
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#endif
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__NR_PAGEFLAGS,
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@ -594,12 +591,6 @@ TESTCLEARFLAG(Young, young, PF_ANY)
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PAGEFLAG(Idle, idle, PF_ANY)
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#endif
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#ifdef CONFIG_KASAN_HW_TAGS
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PAGEFLAG(SkipKASanPoison, skip_kasan_poison, PF_HEAD)
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#else
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PAGEFLAG_FALSE(SkipKASanPoison, skip_kasan_poison)
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#endif
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/*
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* PageReported() is used to track reported free pages within the Buddy
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* allocator. We can use the non-atomic version of the test and set
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@ -55,8 +55,7 @@
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#ifdef CONFIG_KASAN_HW_TAGS
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#define __def_gfpflag_names_kasan , \
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gfpflag_string(__GFP_SKIP_ZERO), \
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gfpflag_string(__GFP_SKIP_KASAN_POISON), \
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gfpflag_string(__GFP_SKIP_KASAN_UNPOISON)
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gfpflag_string(__GFP_SKIP_KASAN)
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#else
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#define __def_gfpflag_names_kasan
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#endif
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@ -96,13 +95,6 @@
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#define IF_HAVE_PG_ARCH_X(_name)
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#endif
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#ifdef CONFIG_KASAN_HW_TAGS
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#define IF_HAVE_PG_SKIP_KASAN_POISON(_name) \
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,{1UL << PG_##_name, __stringify(_name)}
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#else
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#define IF_HAVE_PG_SKIP_KASAN_POISON(_name)
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#endif
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#define DEF_PAGEFLAG_NAME(_name) { 1UL << PG_##_name, __stringify(_name) }
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#define __def_pageflag_names \
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@ -133,8 +125,7 @@ IF_HAVE_PG_HWPOISON(hwpoison) \
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IF_HAVE_PG_IDLE(idle) \
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IF_HAVE_PG_IDLE(young) \
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IF_HAVE_PG_ARCH_X(arch_2) \
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IF_HAVE_PG_ARCH_X(arch_3) \
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IF_HAVE_PG_SKIP_KASAN_POISON(skip_kasan_poison)
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IF_HAVE_PG_ARCH_X(arch_3)
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#define show_page_flags(flags) \
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(flags) ? __print_flags(flags, "|", \
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@ -318,7 +318,7 @@ void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
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* Thus, for VM_ALLOC mappings, hardware tag-based KASAN only tags
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* the first virtual mapping, which is created by vmalloc().
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* Tagging the page_alloc memory backing that vmalloc() allocation is
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* skipped, see ___GFP_SKIP_KASAN_UNPOISON.
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* skipped, see ___GFP_SKIP_KASAN.
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*
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* For non-VM_ALLOC allocations, page_alloc memory is tagged as usual.
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*/
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@ -112,17 +112,6 @@ typedef int __bitwise fpi_t;
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*/
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#define FPI_TO_TAIL ((__force fpi_t)BIT(1))
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/*
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* Don't poison memory with KASAN (only for the tag-based modes).
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* During boot, all non-reserved memblock memory is exposed to page_alloc.
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* Poisoning all that memory lengthens boot time, especially on systems with
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* large amount of RAM. This flag is used to skip that poisoning.
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* This is only done for the tag-based KASAN modes, as those are able to
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* detect memory corruptions with the memory tags assigned by default.
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* All memory allocated normally after boot gets poisoned as usual.
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*/
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#define FPI_SKIP_KASAN_POISON ((__force fpi_t)BIT(2))
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/* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
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static DEFINE_MUTEX(pcp_batch_high_lock);
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#define MIN_PERCPU_PAGELIST_HIGH_FRACTION (8)
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@ -1370,13 +1359,19 @@ static int free_tail_pages_check(struct page *head_page, struct page *page)
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/*
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* Skip KASAN memory poisoning when either:
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*
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* 1. Deferred memory initialization has not yet completed,
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* see the explanation below.
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* 2. Skipping poisoning is requested via FPI_SKIP_KASAN_POISON,
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* see the comment next to it.
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* 3. Skipping poisoning is requested via __GFP_SKIP_KASAN_POISON,
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* see the comment next to it.
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* 4. The allocation is excluded from being checked due to sampling,
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* 1. For generic KASAN: deferred memory initialization has not yet completed.
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* Tag-based KASAN modes skip pages freed via deferred memory initialization
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* using page tags instead (see below).
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* 2. For tag-based KASAN modes: the page has a match-all KASAN tag, indicating
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* that error detection is disabled for accesses via the page address.
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*
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* Pages will have match-all tags in the following circumstances:
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*
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* 1. Pages are being initialized for the first time, including during deferred
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* memory init; see the call to page_kasan_tag_reset in __init_single_page.
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* 2. The allocation was not unpoisoned due to __GFP_SKIP_KASAN, with the
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* exception of pages unpoisoned by kasan_unpoison_vmalloc.
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* 3. The allocation was excluded from being checked due to sampling,
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* see the call to kasan_unpoison_pages.
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*
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* Poisoning pages during deferred memory init will greatly lengthen the
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@ -1392,10 +1387,10 @@ static int free_tail_pages_check(struct page *head_page, struct page *page)
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*/
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static inline bool should_skip_kasan_poison(struct page *page, fpi_t fpi_flags)
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{
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return deferred_pages_enabled() ||
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(!IS_ENABLED(CONFIG_KASAN_GENERIC) &&
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(fpi_flags & FPI_SKIP_KASAN_POISON)) ||
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PageSkipKASanPoison(page);
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if (IS_ENABLED(CONFIG_KASAN_GENERIC))
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return deferred_pages_enabled();
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return page_kasan_tag(page) == 0xff;
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}
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static void kernel_init_pages(struct page *page, int numpages)
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@ -1730,7 +1725,7 @@ void __free_pages_core(struct page *page, unsigned int order)
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* Bypass PCP and place fresh pages right to the tail, primarily
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* relevant for memory onlining.
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*/
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__free_pages_ok(page, order, FPI_TO_TAIL | FPI_SKIP_KASAN_POISON);
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__free_pages_ok(page, order, FPI_TO_TAIL);
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}
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#ifdef CONFIG_NUMA
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@ -2396,9 +2391,9 @@ static inline bool should_skip_kasan_unpoison(gfp_t flags)
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/*
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* With hardware tag-based KASAN enabled, skip if this has been
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* requested via __GFP_SKIP_KASAN_UNPOISON.
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* requested via __GFP_SKIP_KASAN.
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*/
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return flags & __GFP_SKIP_KASAN_UNPOISON;
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return flags & __GFP_SKIP_KASAN;
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}
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static inline bool should_skip_init(gfp_t flags)
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@ -2417,7 +2412,6 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
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bool init = !want_init_on_free() && want_init_on_alloc(gfp_flags) &&
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!should_skip_init(gfp_flags);
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bool zero_tags = init && (gfp_flags & __GFP_ZEROTAGS);
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bool reset_tags = true;
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int i;
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set_page_private(page, 0);
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@ -2451,37 +2445,22 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
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/* Take note that memory was initialized by the loop above. */
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init = false;
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}
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if (!should_skip_kasan_unpoison(gfp_flags)) {
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/* Try unpoisoning (or setting tags) and initializing memory. */
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if (kasan_unpoison_pages(page, order, init)) {
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/* Take note that memory was initialized by KASAN. */
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if (kasan_has_integrated_init())
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init = false;
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/* Take note that memory tags were set by KASAN. */
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reset_tags = false;
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} else {
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/*
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* KASAN decided to exclude this allocation from being
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* (un)poisoned due to sampling. Make KASAN skip
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* poisoning when the allocation is freed.
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*/
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SetPageSkipKASanPoison(page);
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}
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}
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/*
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* If memory tags have not been set by KASAN, reset the page tags to
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* ensure page_address() dereferencing does not fault.
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*/
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if (reset_tags) {
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if (!should_skip_kasan_unpoison(gfp_flags) &&
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kasan_unpoison_pages(page, order, init)) {
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/* Take note that memory was initialized by KASAN. */
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if (kasan_has_integrated_init())
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init = false;
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} else {
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/*
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* If memory tags have not been set by KASAN, reset the page
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* tags to ensure page_address() dereferencing does not fault.
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*/
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for (i = 0; i != 1 << order; ++i)
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page_kasan_tag_reset(page + i);
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}
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/* If memory is still not initialized, initialize it now. */
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if (init)
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kernel_init_pages(page, 1 << order);
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/* Propagate __GFP_SKIP_KASAN_POISON to page flags. */
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if (kasan_hw_tags_enabled() && (gfp_flags & __GFP_SKIP_KASAN_POISON))
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SetPageSkipKASanPoison(page);
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set_page_owner(page, order, gfp_flags);
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page_table_check_alloc(page, order);
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@ -3188,7 +3188,7 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
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* pages backing VM_ALLOC mapping. Memory is instead
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* poisoned and zeroed by kasan_unpoison_vmalloc().
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*/
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gfp_mask |= __GFP_SKIP_KASAN_UNPOISON | __GFP_SKIP_ZERO;
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gfp_mask |= __GFP_SKIP_KASAN | __GFP_SKIP_ZERO;
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}
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/* Take note that the mapping is PAGE_KERNEL. */
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