| Message ID | 9ed583c1a3acf014987e3aef12249506c1c69146.1560339705.git.andreyknvl@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | arm64: untag user pointers passed to the kernel | expand |
On 12/06/2019 12:43, Andrey Konovalov wrote: > This patch is a part of a series that extends arm64 kernel ABI to allow to > pass tagged user pointers (with the top byte set to something else other > than 0x00) as syscall arguments. > > copy_from_user (and a few other similar functions) are used to copy data > from user memory into the kernel memory or vice versa. Since a user can > provided a tagged pointer to one of the syscalls that use copy_from_user, > we need to correctly handle such pointers. > > Do this by untagging user pointers in access_ok and in __uaccess_mask_ptr, > before performing access validity checks. > > Note, that this patch only temporarily untags the pointers to perform the > checks, but then passes them as is into the kernel internals. > > Reviewed-by: Kees Cook <keescook@chromium.org> > Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> > --- > arch/arm64/include/asm/uaccess.h | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h > index e5d5f31c6d36..df729afca0ba 100644 > --- a/arch/arm64/include/asm/uaccess.h > +++ b/arch/arm64/include/asm/uaccess.h > @@ -73,6 +73,8 @@ static inline unsigned long __range_ok(const void __user *addr, unsigned long si > { > unsigned long ret, limit = current_thread_info()->addr_limit; > > + addr = untagged_addr(addr); > + > __chk_user_ptr(addr); > asm volatile( > // A + B <= C + 1 for all A,B,C, in four easy steps: > @@ -226,7 +228,8 @@ static inline void uaccess_enable_not_uao(void) > > /* > * Sanitise a uaccess pointer such that it becomes NULL if above the > - * current addr_limit. > + * current addr_limit. In case the pointer is tagged (has the top byte set), > + * untag the pointer before checking. > */ > #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr) > static inline void __user *__uaccess_mask_ptr(const void __user *ptr) > @@ -234,10 +237,11 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr) > void __user *safe_ptr; > > asm volatile( > - " bics xzr, %1, %2\n" > + " bics xzr, %3, %2\n" > " csel %0, %1, xzr, eq\n" > : "=&r" (safe_ptr) > - : "r" (ptr), "r" (current_thread_info()->addr_limit) > + : "r" (ptr), "r" (current_thread_info()->addr_limit), > + "r" (untagged_addr(ptr)) > : "cc"); > > csdb(); >
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h index e5d5f31c6d36..df729afca0ba 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -73,6 +73,8 @@ static inline unsigned long __range_ok(const void __user *addr, unsigned long si { unsigned long ret, limit = current_thread_info()->addr_limit; + addr = untagged_addr(addr); + __chk_user_ptr(addr); asm volatile( // A + B <= C + 1 for all A,B,C, in four easy steps: @@ -226,7 +228,8 @@ static inline void uaccess_enable_not_uao(void) /* * Sanitise a uaccess pointer such that it becomes NULL if above the - * current addr_limit. + * current addr_limit. In case the pointer is tagged (has the top byte set), + * untag the pointer before checking. */ #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr) static inline void __user *__uaccess_mask_ptr(const void __user *ptr) @@ -234,10 +237,11 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr) void __user *safe_ptr; asm volatile( - " bics xzr, %1, %2\n" + " bics xzr, %3, %2\n" " csel %0, %1, xzr, eq\n" : "=&r" (safe_ptr) - : "r" (ptr), "r" (current_thread_info()->addr_limit) + : "r" (ptr), "r" (current_thread_info()->addr_limit), + "r" (untagged_addr(ptr)) : "cc"); csdb();