From 81895a65ec63ee1daec3255dc1a06675d2fbe915 Mon Sep 17 00:00:00 2001 From: Jason A. Donenfeld Date: Wed, 5 Oct 2022 16:43:38 +0200 Subject: treewide: use prandom_u32_max() when possible, part 1 Rather than incurring a division or requesting too many random bytes for the given range, use the prandom_u32_max() function, which only takes the minimum required bytes from the RNG and avoids divisions. This was done mechanically with this coccinelle script: @basic@ expression E; type T; identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32"; typedef u64; @@ ( - ((T)get_random_u32() % (E)) + prandom_u32_max(E) | - ((T)get_random_u32() & ((E) - 1)) + prandom_u32_max(E * XXX_MAKE_SURE_E_IS_POW2) | - ((u64)(E) * get_random_u32() >> 32) + prandom_u32_max(E) | - ((T)get_random_u32() & ~PAGE_MASK) + prandom_u32_max(PAGE_SIZE) ) @multi_line@ identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32"; identifier RAND; expression E; @@ - RAND = get_random_u32(); ... when != RAND - RAND %= (E); + RAND = prandom_u32_max(E); // Find a potential literal @literal_mask@ expression LITERAL; type T; identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32"; position p; @@ ((T)get_random_u32()@p & (LITERAL)) // Add one to the literal. @script:python add_one@ literal << literal_mask.LITERAL; RESULT; @@ value = None if literal.startswith('0x'): value = int(literal, 16) elif literal[0] in '123456789': value = int(literal, 10) if value is None: print("I don't know how to handle %s" % (literal)) cocci.include_match(False) elif value == 2**32 - 1 or value == 2**31 - 1 or value == 2**24 - 1 or value == 2**16 - 1 or value == 2**8 - 1: print("Skipping 0x%x for cleanup elsewhere" % (value)) cocci.include_match(False) elif value & (value + 1) != 0: print("Skipping 0x%x because it's not a power of two minus one" % (value)) cocci.include_match(False) elif literal.startswith('0x'): coccinelle.RESULT = cocci.make_expr("0x%x" % (value + 1)) else: coccinelle.RESULT = cocci.make_expr("%d" % (value + 1)) // Replace the literal mask with the calculated result. @plus_one@ expression literal_mask.LITERAL; position literal_mask.p; expression add_one.RESULT; identifier FUNC; @@ - (FUNC()@p & (LITERAL)) + prandom_u32_max(RESULT) @collapse_ret@ type T; identifier VAR; expression E; @@ { - T VAR; - VAR = (E); - return VAR; + return E; } @drop_var@ type T; identifier VAR; @@ { - T VAR; ... when != VAR } Reviewed-by: Greg Kroah-Hartman Reviewed-by: Kees Cook Reviewed-by: Yury Norov Reviewed-by: KP Singh Reviewed-by: Jan Kara # for ext4 and sbitmap Reviewed-by: Christoph Böhmwalder # for drbd Acked-by: Jakub Kicinski Acked-by: Heiko Carstens # for s390 Acked-by: Ulf Hansson # for mmc Acked-by: Darrick J. Wong # for xfs Signed-off-by: Jason A. Donenfeld --- arch/arm/kernel/process.c | 2 +- arch/arm64/kernel/process.c | 2 +- arch/loongarch/kernel/process.c | 2 +- arch/loongarch/kernel/vdso.c | 2 +- arch/mips/kernel/process.c | 2 +- arch/mips/kernel/vdso.c | 2 +- arch/parisc/kernel/vdso.c | 2 +- arch/powerpc/kernel/process.c | 2 +- arch/s390/kernel/process.c | 2 +- arch/s390/kernel/vdso.c | 2 +- arch/sparc/vdso/vma.c | 2 +- arch/um/kernel/process.c | 2 +- arch/x86/entry/vdso/vma.c | 2 +- arch/x86/kernel/module.c | 2 +- arch/x86/kernel/process.c | 2 +- arch/x86/mm/pat/cpa-test.c | 4 ++-- 16 files changed, 17 insertions(+), 17 deletions(-) (limited to 'arch') diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index 96f3fbd51764..129279b33b1d 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -375,7 +375,7 @@ static unsigned long sigpage_addr(const struct mm_struct *mm, slots = ((last - first) >> PAGE_SHIFT) + 1; - offset = get_random_int() % slots; + offset = prandom_u32_max(slots); addr = first + (offset << PAGE_SHIFT); diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 92bcc1768f0b..87203429f802 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -595,7 +595,7 @@ unsigned long __get_wchan(struct task_struct *p) unsigned long arch_align_stack(unsigned long sp) { if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) - sp -= get_random_int() & ~PAGE_MASK; + sp -= prandom_u32_max(PAGE_SIZE); return sp & ~0xf; } diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c index 660492f064e7..1256e3582475 100644 --- a/arch/loongarch/kernel/process.c +++ b/arch/loongarch/kernel/process.c @@ -293,7 +293,7 @@ unsigned long stack_top(void) unsigned long arch_align_stack(unsigned long sp) { if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) - sp -= get_random_int() & ~PAGE_MASK; + sp -= prandom_u32_max(PAGE_SIZE); return sp & STACK_ALIGN; } diff --git a/arch/loongarch/kernel/vdso.c b/arch/loongarch/kernel/vdso.c index f32c38abd791..8c9826062652 100644 --- a/arch/loongarch/kernel/vdso.c +++ b/arch/loongarch/kernel/vdso.c @@ -78,7 +78,7 @@ static unsigned long vdso_base(void) unsigned long base = STACK_TOP; if (current->flags & PF_RANDOMIZE) { - base += get_random_int() & (VDSO_RANDOMIZE_SIZE - 1); + base += prandom_u32_max(VDSO_RANDOMIZE_SIZE); base = PAGE_ALIGN(base); } diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c index 35b912bce429..bbe9ce471791 100644 --- a/arch/mips/kernel/process.c +++ b/arch/mips/kernel/process.c @@ -711,7 +711,7 @@ unsigned long mips_stack_top(void) unsigned long arch_align_stack(unsigned long sp) { if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) - sp -= get_random_int() & ~PAGE_MASK; + sp -= prandom_u32_max(PAGE_SIZE); return sp & ALMASK; } diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c index b2cc2c2dd4bf..5fd9bf1d596c 100644 --- a/arch/mips/kernel/vdso.c +++ b/arch/mips/kernel/vdso.c @@ -79,7 +79,7 @@ static unsigned long vdso_base(void) } if (current->flags & PF_RANDOMIZE) { - base += get_random_int() & (VDSO_RANDOMIZE_SIZE - 1); + base += prandom_u32_max(VDSO_RANDOMIZE_SIZE); base = PAGE_ALIGN(base); } diff --git a/arch/parisc/kernel/vdso.c b/arch/parisc/kernel/vdso.c index 63dc44c4c246..47e5960a2f96 100644 --- a/arch/parisc/kernel/vdso.c +++ b/arch/parisc/kernel/vdso.c @@ -75,7 +75,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, map_base = mm->mmap_base; if (current->flags & PF_RANDOMIZE) - map_base -= (get_random_int() & 0x1f) * PAGE_SIZE; + map_base -= prandom_u32_max(0x20) * PAGE_SIZE; vdso_text_start = get_unmapped_area(NULL, map_base, vdso_text_len, 0, 0); diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 37df0428e4fb..599391c23573 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -2308,6 +2308,6 @@ void notrace __ppc64_runlatch_off(void) unsigned long arch_align_stack(unsigned long sp) { if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) - sp -= get_random_int() & ~PAGE_MASK; + sp -= prandom_u32_max(PAGE_SIZE); return sp & ~0xf; } diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c index d5119e039d85..5ec78555dd2e 100644 --- a/arch/s390/kernel/process.c +++ b/arch/s390/kernel/process.c @@ -224,7 +224,7 @@ unsigned long __get_wchan(struct task_struct *p) unsigned long arch_align_stack(unsigned long sp) { if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) - sp -= get_random_int() & ~PAGE_MASK; + sp -= prandom_u32_max(PAGE_SIZE); return sp & ~0xf; } diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c index 535099f2736d..3105ca5bd470 100644 --- a/arch/s390/kernel/vdso.c +++ b/arch/s390/kernel/vdso.c @@ -227,7 +227,7 @@ static unsigned long vdso_addr(unsigned long start, unsigned long len) end -= len; if (end > start) { - offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1); + offset = prandom_u32_max(((end - start) >> PAGE_SHIFT) + 1); addr = start + (offset << PAGE_SHIFT); } else { addr = start; diff --git a/arch/sparc/vdso/vma.c b/arch/sparc/vdso/vma.c index cc19e09b0fa1..ae9a86cb6f3d 100644 --- a/arch/sparc/vdso/vma.c +++ b/arch/sparc/vdso/vma.c @@ -354,7 +354,7 @@ static unsigned long vdso_addr(unsigned long start, unsigned int len) unsigned int offset; /* This loses some more bits than a modulo, but is cheaper */ - offset = get_random_int() & (PTRS_PER_PTE - 1); + offset = prandom_u32_max(PTRS_PER_PTE); return start + (offset << PAGE_SHIFT); } diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c index 80b90b1276a1..010bc422a09d 100644 --- a/arch/um/kernel/process.c +++ b/arch/um/kernel/process.c @@ -356,7 +356,7 @@ int singlestepping(void * t) unsigned long arch_align_stack(unsigned long sp) { if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) - sp -= get_random_int() % 8192; + sp -= prandom_u32_max(8192); return sp & ~0xf; } #endif diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index 6292b960037b..311eae30e089 100644 --- a/arch/x86/entry/vdso/vma.c +++ b/arch/x86/entry/vdso/vma.c @@ -327,7 +327,7 @@ static unsigned long vdso_addr(unsigned long start, unsigned len) end -= len; if (end > start) { - offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1); + offset = prandom_u32_max(((end - start) >> PAGE_SHIFT) + 1); addr = start + (offset << PAGE_SHIFT); } else { addr = start; diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c index b1abf663417c..c032edcd3d95 100644 --- a/arch/x86/kernel/module.c +++ b/arch/x86/kernel/module.c @@ -53,7 +53,7 @@ static unsigned long int get_module_load_offset(void) */ if (module_load_offset == 0) module_load_offset = - (get_random_int() % 1024 + 1) * PAGE_SIZE; + (prandom_u32_max(1024) + 1) * PAGE_SIZE; mutex_unlock(&module_kaslr_mutex); } return module_load_offset; diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 58a6ea472db9..c21b7347a26d 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -965,7 +965,7 @@ early_param("idle", idle_setup); unsigned long arch_align_stack(unsigned long sp) { if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) - sp -= get_random_int() % 8192; + sp -= prandom_u32_max(8192); return sp & ~0xf; } diff --git a/arch/x86/mm/pat/cpa-test.c b/arch/x86/mm/pat/cpa-test.c index 0612a73638a8..423b21e80929 100644 --- a/arch/x86/mm/pat/cpa-test.c +++ b/arch/x86/mm/pat/cpa-test.c @@ -136,10 +136,10 @@ static int pageattr_test(void) failed += print_split(&sa); for (i = 0; i < NTEST; i++) { - unsigned long pfn = prandom_u32() % max_pfn_mapped; + unsigned long pfn = prandom_u32_max(max_pfn_mapped); addr[i] = (unsigned long)__va(pfn << PAGE_SHIFT); - len[i] = prandom_u32() % NPAGES; + len[i] = prandom_u32_max(NPAGES); len[i] = min_t(unsigned long, len[i], max_pfn_mapped - pfn - 1); if (len[i] == 0) -- cgit v1.2.3