| Message ID | 20230329193931.320642-3-dev@der-flo.net (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | Fix copy_from_user_nofault() | expand |
On Wed, Mar 29, 2023 at 09:39:33PM +0200, Florian Lehner wrote: > From: Alexei Starovoitov <ast@kernel.org> > > 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@kernel.org> > --- > 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 ++++++++++++++++++++++----- > mm/usercopy.c | 2 +- > 6 files changed, 42 insertions(+), 83 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 8fc15ed5e60b..b1e27ca28563 100644 > --- a/arch/x86/include/asm/perf_event.h > +++ b/arch/x86/include/asm/perf_event.h > @@ -598,6 +598,4 @@ static __always_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; > } > diff --git a/mm/usercopy.c b/mm/usercopy.c > index 4c3164beacec..83c164aba6e0 100644 > --- a/mm/usercopy.c > +++ b/mm/usercopy.c > @@ -173,7 +173,7 @@ static inline void check_heap_object(const void *ptr, unsigned long n, > return; > } > > - if (is_vmalloc_addr(ptr)) { > + if (is_vmalloc_addr(ptr) && !pagefault_disabled()) { Florian, thank you for taking over the patches. This bit isn't right though. This hunk needs to be in patch 1. Then instead of open coding __copy_from_user_inatomic without check_object_size() it would be fine to only add __access_ok and nmi_uaccess_okay() to copy_from_user_nofault() and keep __copy_from_user_inatomic(). The patch 2 can still remove copy_from_user_nmi() (adjusting return value, of course), since check_heap_object() will no longer dead lock due to !pagefault_disabled() in the patch 1. Does this make sense?
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h index 8fc15ed5e60b..b1e27ca28563 100644 --- a/arch/x86/include/asm/perf_event.h +++ b/arch/x86/include/asm/perf_event.h @@ -598,6 +598,4 @@ static __always_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; } diff --git a/mm/usercopy.c b/mm/usercopy.c index 4c3164beacec..83c164aba6e0 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -173,7 +173,7 @@ static inline void check_heap_object(const void *ptr, unsigned long n, return; } - if (is_vmalloc_addr(ptr)) { + if (is_vmalloc_addr(ptr) && !pagefault_disabled()) { struct vmap_area *area = find_vmap_area(addr); if (!area)