From 3d13f313ce4c34c524ccc37986fe77172f601ff3 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 11 Aug 2020 18:33:47 -0700 Subject: uaccess: add force_uaccess_{begin,end} helpers Add helpers to wrap the get_fs/set_fs magic for undoing any damange done by set_fs(KERNEL_DS). There is no real functional benefit, but this documents the intent of these calls better, and will allow stubbing the functions out easily for kernels builds that do not allow address space overrides in the future. [hch@lst.de: drop two incorrect hunks, fix a commit log typo] Link: http://lkml.kernel.org/r/20200714105505.935079-6-hch@lst.de Signed-off-by: Christoph Hellwig Signed-off-by: Andrew Morton Acked-by: Linus Torvalds Acked-by: Mark Rutland Acked-by: Greentime Hu Acked-by: Geert Uytterhoeven Cc: Nick Hu Cc: Vincent Chen Cc: Paul Walmsley Cc: Palmer Dabbelt Link: http://lkml.kernel.org/r/20200710135706.537715-6-hch@lst.de Signed-off-by: Linus Torvalds --- mm/maccess.c | 22 ++++++++++------------ 1 file changed, 10 insertions(+), 12 deletions(-) (limited to 'mm/maccess.c') diff --git a/mm/maccess.c b/mm/maccess.c index f98ff91e32c6..3bd70405f2d8 100644 --- a/mm/maccess.c +++ b/mm/maccess.c @@ -205,15 +205,14 @@ long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count) long copy_from_user_nofault(void *dst, const void __user *src, size_t size) { long ret = -EFAULT; - mm_segment_t old_fs = get_fs(); + mm_segment_t old_fs = force_uaccess_begin(); - set_fs(USER_DS); if (access_ok(src, size)) { pagefault_disable(); ret = __copy_from_user_inatomic(dst, src, size); pagefault_enable(); } - set_fs(old_fs); + force_uaccess_end(old_fs); if (ret) return -EFAULT; @@ -233,15 +232,14 @@ EXPORT_SYMBOL_GPL(copy_from_user_nofault); long copy_to_user_nofault(void __user *dst, const void *src, size_t size) { long ret = -EFAULT; - mm_segment_t old_fs = get_fs(); + mm_segment_t old_fs = force_uaccess_begin(); - set_fs(USER_DS); if (access_ok(dst, size)) { pagefault_disable(); ret = __copy_to_user_inatomic(dst, src, size); pagefault_enable(); } - set_fs(old_fs); + force_uaccess_end(old_fs); if (ret) return -EFAULT; @@ -270,17 +268,17 @@ EXPORT_SYMBOL_GPL(copy_to_user_nofault); long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr, long count) { - mm_segment_t old_fs = get_fs(); + mm_segment_t old_fs; long ret; if (unlikely(count <= 0)) return 0; - set_fs(USER_DS); + old_fs = force_uaccess_begin(); pagefault_disable(); ret = strncpy_from_user(dst, unsafe_addr, count); pagefault_enable(); - set_fs(old_fs); + force_uaccess_end(old_fs); if (ret >= count) { ret = count; @@ -310,14 +308,14 @@ long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr, */ long strnlen_user_nofault(const void __user *unsafe_addr, long count) { - mm_segment_t old_fs = get_fs(); + mm_segment_t old_fs; int ret; - set_fs(USER_DS); + old_fs = force_uaccess_begin(); pagefault_disable(); ret = strnlen_user(unsafe_addr, count); pagefault_enable(); - set_fs(old_fs); + force_uaccess_end(old_fs); return ret; } -- cgit v1.2.3