From: Alexei Starovoitov <ast@xxxxxxxxxx> There are several issues with arch_perf_out_copy_user(). On x86 it's the same as copy_from_user_nmi() and all is good, but on other archs: - __access_ok() is missing. Only on m68k, s390, parisc, sparc64 archs this function returns 'true'. Other archs must call it before user memory access. - nmi_uaccess_okay() is missing. - __copy_from_user_inatomic() issues under CONFIG_HARDENED_USERCOPY. The latter two issues existed in copy_from_user_nofault() as well and were fixed in the previous patch. This patch copies comments from copy_from_user_nmi() into mm/maccess.c and splits copy_from_user_nofault() into copy_from_user_nmi() that returns number of not copied bytes and copy_from_user_nofault() that returns -EFAULT or zero. With that copy_from_user_nmi() becomes generic and is used by perf on all architectures. Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> --- arch/x86/include/asm/perf_event.h | 2 -- arch/x86/lib/Makefile | 2 +- arch/x86/lib/usercopy.c | 55 ------------------------------- kernel/events/internal.h | 16 +-------- mm/maccess.c | 48 ++++++++++++++++++++++----- 5 files changed, 41 insertions(+), 82 deletions(-) delete mode 100644 arch/x86/lib/usercopy.c diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h index 5d0f6891ae61..2e5cada5f74e 100644 --- a/arch/x86/include/asm/perf_event.h +++ b/arch/x86/include/asm/perf_event.h @@ -590,6 +590,4 @@ static inline void perf_lopwr_cb(bool lopwr_in) static inline void amd_pmu_disable_virt(void) { } #endif -#define arch_perf_out_copy_user copy_from_user_nmi - #endif /* _ASM_X86_PERF_EVENT_H */ diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile index 4f1a40a86534..e85937696afd 100644 --- a/arch/x86/lib/Makefile +++ b/arch/x86/lib/Makefile @@ -42,7 +42,7 @@ clean-files := inat-tables.c obj-$(CONFIG_SMP) += msr-smp.o cache-smp.o lib-y := delay.o misc.o cmdline.o cpu.o -lib-y += usercopy_$(BITS).o usercopy.o getuser.o putuser.o +lib-y += usercopy_$(BITS).o getuser.o putuser.o lib-y += memcpy_$(BITS).o lib-y += pc-conf-reg.o lib-$(CONFIG_ARCH_HAS_COPY_MC) += copy_mc.o copy_mc_64.o diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c deleted file mode 100644 index 24b48af27417..000000000000 --- a/arch/x86/lib/usercopy.c +++ /dev/null @@ -1,55 +0,0 @@ -/* - * User address space access functions. - * - * For licencing details see kernel-base/COPYING - */ - -#include <linux/uaccess.h> -#include <linux/export.h> -#include <linux/instrumented.h> - -#include <asm/tlbflush.h> - -/** - * copy_from_user_nmi - NMI safe copy from user - * @to: Pointer to the destination buffer - * @from: Pointer to a user space address of the current task - * @n: Number of bytes to copy - * - * Returns: The number of not copied bytes. 0 is success, i.e. all bytes copied - * - * Contrary to other copy_from_user() variants this function can be called - * from NMI context. Despite the name it is not restricted to be called - * from NMI context. It is safe to be called from any other context as - * well. It disables pagefaults across the copy which means a fault will - * abort the copy. - * - * For NMI context invocations this relies on the nested NMI work to allow - * atomic faults from the NMI path; the nested NMI paths are careful to - * preserve CR2. - */ -unsigned long -copy_from_user_nmi(void *to, const void __user *from, unsigned long n) -{ - unsigned long ret; - - if (!__access_ok(from, n)) - return n; - - if (!nmi_uaccess_okay()) - return n; - - /* - * Even though this function is typically called from NMI/IRQ context - * disable pagefaults so that its behaviour is consistent even when - * called from other contexts. - */ - pagefault_disable(); - instrument_copy_from_user_before(to, from, n); - ret = raw_copy_from_user(to, from, n); - instrument_copy_from_user_after(to, from, n, ret); - pagefault_enable(); - - return ret; -} -EXPORT_SYMBOL_GPL(copy_from_user_nmi); diff --git a/kernel/events/internal.h b/kernel/events/internal.h index 5150d5f84c03..62fe2089a1f9 100644 --- a/kernel/events/internal.h +++ b/kernel/events/internal.h @@ -190,21 +190,7 @@ memcpy_skip(void *dst, const void *src, unsigned long n) DEFINE_OUTPUT_COPY(__output_skip, memcpy_skip) -#ifndef arch_perf_out_copy_user -#define arch_perf_out_copy_user arch_perf_out_copy_user - -static inline unsigned long -arch_perf_out_copy_user(void *dst, const void *src, unsigned long n) -{ - unsigned long ret; - - pagefault_disable(); - ret = __copy_from_user_inatomic(dst, src, n); - pagefault_enable(); - - return ret; -} -#endif +#define arch_perf_out_copy_user copy_from_user_nmi DEFINE_OUTPUT_COPY(__output_copy_user, arch_perf_out_copy_user) diff --git a/mm/maccess.c b/mm/maccess.c index 6ee9b337c501..aa7520bb64bf 100644 --- a/mm/maccess.c +++ b/mm/maccess.c @@ -103,17 +103,27 @@ long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count) } /** - * copy_from_user_nofault(): safely attempt to read from a user-space location - * @dst: pointer to the buffer that shall take the data - * @src: address to read from. This must be a user address. - * @size: size of the data chunk + * copy_from_user_nmi - NMI safe copy from user + * @dst: Pointer to the destination buffer + * @src: Pointer to a user space address of the current task + * @size: Number of bytes to copy * - * Safely read from user address @src to the buffer at @dst. If a kernel fault - * happens, handle that and return -EFAULT. + * Returns: The number of not copied bytes. 0 is success, i.e. all bytes copied + * + * Contrary to other copy_from_user() variants this function can be called + * from NMI context. Despite the name it is not restricted to be called + * from NMI context. It is safe to be called from any other context as + * well. It disables pagefaults across the copy which means a fault will + * abort the copy. + * + * For NMI context invocations this relies on the nested NMI work to allow + * atomic faults from the NMI path; the nested NMI paths are careful to + * preserve CR2 on X86 architecture. */ -long copy_from_user_nofault(void *dst, const void __user *src, size_t size) +unsigned long +copy_from_user_nmi(void *dst, const void __user *src, unsigned long size) { - long ret = -EFAULT; + unsigned long ret = size; if (!__access_ok(src, size)) return ret; @@ -121,13 +131,33 @@ long copy_from_user_nofault(void *dst, const void __user *src, size_t size) if (!nmi_uaccess_okay()) return ret; + /* + * Even though this function is typically called from NMI/IRQ context + * disable pagefaults so that its behaviour is consistent even when + * called from other contexts. + */ pagefault_disable(); instrument_copy_from_user_before(dst, src, size); ret = raw_copy_from_user(dst, src, size); instrument_copy_from_user_after(dst, src, size, ret); pagefault_enable(); - if (ret) + return ret; +} +EXPORT_SYMBOL_GPL(copy_from_user_nmi); + +/** + * copy_from_user_nofault(): safely attempt to read from a user-space location + * @dst: pointer to the buffer that shall take the data + * @src: address to read from. This must be a user address. + * @size: size of the data chunk + * + * Safely read from user address @src to the buffer at @dst. If a kernel fault + * happens, handle that and return -EFAULT. + */ +long copy_from_user_nofault(void *dst, const void __user *src, size_t size) +{ + if (copy_from_user_nmi(dst, src, size)) return -EFAULT; return 0; } -- 2.30.2