| Message ID | 20181010155544.19125-1-james.morse@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Revert "arm64: uaccess: implement unsafe accessors" | expand |
On 10/10/18 16:55, James Morse wrote: > This reverts commit a1f33941f7e103bcf471eaf8461b212223c642d6. > > The unsafe accessors allow the PAN enable/disable calls to be made > once for a group of accesses. Adding these means we can now have > sequences that look like this: > > | user_access_begin(); > | unsafe_put_user(static-value, x, err); > | unsafe_put_user(helper-that-sleeps(), x, err); > | user_access_end(); > > Calling schedule() without taking an exception doesn't switch the > PSTATE or TTBRs. We can switch out of a uaccess-enabled region, and > run other code with uaccess enabled for a different thread. > > We can also switch from uaccess-disabled code back into this region, > meaning the unsafe_put_user()s will fault. > > For software-PAN, threads that do this will get stuck as > handle_mm_fault() will determine the page has already been mapped in, > but we fault again as the page tables aren't loaded. > > To solve this we need code in __switch_to() that save/restores the > PAN state. > > Signed-off-by: James Morse <james.morse@arm.com> > CC: Julien Thierry <julien.thierry@arm.com> > Acked-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Julien Thierry <julien.thierry@arm.com> > --- > This reverts a patch queued in for-next/core. > > arch/arm64/include/asm/uaccess.h | 61 ++++++++------------------------ > 1 file changed, 15 insertions(+), 46 deletions(-) > > diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h > index 8ac6e34922e7..07c34087bd5e 100644 > --- a/arch/arm64/include/asm/uaccess.h > +++ b/arch/arm64/include/asm/uaccess.h > @@ -276,9 +276,11 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr) > : "+r" (err), "=&r" (x) \ > : "r" (addr), "i" (-EFAULT)) > > -#define __get_user_err_unsafe(x, ptr, err) \ > +#define __get_user_err(x, ptr, err) \ > do { \ > unsigned long __gu_val; \ > + __chk_user_ptr(ptr); \ > + uaccess_enable_not_uao(); \ > switch (sizeof(*(ptr))) { \ > case 1: \ > __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr), \ > @@ -299,24 +301,17 @@ do { \ > default: \ > BUILD_BUG(); \ > } \ > - (x) = (__force __typeof__(*(ptr)))__gu_val; \ > -} while (0) > - > -#define __get_user_err_check(x, ptr, err) \ > -do { \ > - __chk_user_ptr(ptr); \ > - uaccess_enable_not_uao(); \ > - __get_user_err_unsafe((x), (ptr), (err)); \ > uaccess_disable_not_uao(); \ > + (x) = (__force __typeof__(*(ptr)))__gu_val; \ > } while (0) > > -#define __get_user_err(x, ptr, err, accessor) \ > +#define __get_user_check(x, ptr, err) \ > ({ \ > __typeof__(*(ptr)) __user *__p = (ptr); \ > might_fault(); \ > if (access_ok(VERIFY_READ, __p, sizeof(*__p))) { \ > __p = uaccess_mask_ptr(__p); \ > - accessor((x), __p, (err)); \ > + __get_user_err((x), __p, (err)); \ > } else { \ > (x) = 0; (err) = -EFAULT; \ > } \ > @@ -324,14 +319,14 @@ do { \ > > #define __get_user_error(x, ptr, err) \ > ({ \ > - __get_user_err((x), (ptr), (err), __get_user_err_check); \ > + __get_user_check((x), (ptr), (err)); \ > (void)0; \ > }) > > #define __get_user(x, ptr) \ > ({ \ > int __gu_err = 0; \ > - __get_user_err((x), (ptr), __gu_err, __get_user_err_check); \ > + __get_user_check((x), (ptr), __gu_err); \ > __gu_err; \ > }) > > @@ -351,9 +346,11 @@ do { \ > : "+r" (err) \ > : "r" (x), "r" (addr), "i" (-EFAULT)) > > -#define __put_user_err_unsafe(x, ptr, err) \ > +#define __put_user_err(x, ptr, err) \ > do { \ > __typeof__(*(ptr)) __pu_val = (x); \ > + __chk_user_ptr(ptr); \ > + uaccess_enable_not_uao(); \ > switch (sizeof(*(ptr))) { \ > case 1: \ > __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr), \ > @@ -374,24 +371,16 @@ do { \ > default: \ > BUILD_BUG(); \ > } \ > -} while (0) > - > - > -#define __put_user_err_check(x, ptr, err) \ > -do { \ > - __chk_user_ptr(ptr); \ > - uaccess_enable_not_uao(); \ > - __put_user_err_unsafe((x), (ptr), (err)); \ > uaccess_disable_not_uao(); \ > } while (0) > > -#define __put_user_err(x, ptr, err, accessor) \ > +#define __put_user_check(x, ptr, err) \ > ({ \ > __typeof__(*(ptr)) __user *__p = (ptr); \ > might_fault(); \ > if (access_ok(VERIFY_WRITE, __p, sizeof(*__p))) { \ > __p = uaccess_mask_ptr(__p); \ > - accessor((x), __p, (err)); \ > + __put_user_err((x), __p, (err)); \ > } else { \ > (err) = -EFAULT; \ > } \ > @@ -399,39 +388,19 @@ do { \ > > #define __put_user_error(x, ptr, err) \ > ({ \ > - __put_user_err((x), (ptr), (err), __put_user_err_check); \ > + __put_user_check((x), (ptr), (err)); \ > (void)0; \ > }) > > #define __put_user(x, ptr) \ > ({ \ > int __pu_err = 0; \ > - __put_user_err((x), (ptr), __pu_err, __put_user_err_check); \ > + __put_user_check((x), (ptr), __pu_err); \ > __pu_err; \ > }) > > #define put_user __put_user > > - > -#define user_access_begin() uaccess_enable_not_uao() > -#define user_access_end() uaccess_disable_not_uao() > - > -#define unsafe_get_user(x, ptr, err) \ > -do { \ > - int __gu_err = 0; \ > - __get_user_err((x), (ptr), __gu_err, __get_user_err_unsafe); \ > - if (__gu_err != 0) \ > - goto err; \ > -} while (0) > - > -#define unsafe_put_user(x, ptr, err) \ > -do { \ > - int __pu_err = 0; \ > - __put_user_err((x), (ptr), __pu_err, __put_user_err_unsafe); \ > - if (__pu_err != 0) \ > - goto err; \ > -} while (0) > - > extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n); > #define raw_copy_from_user(to, from, n) \ > ({ \ >
On Wed, Oct 10, 2018 at 04:55:44PM +0100, James Morse wrote: > This reverts commit a1f33941f7e103bcf471eaf8461b212223c642d6. > > The unsafe accessors allow the PAN enable/disable calls to be made > once for a group of accesses. Adding these means we can now have > sequences that look like this: > > | user_access_begin(); > | unsafe_put_user(static-value, x, err); > | unsafe_put_user(helper-that-sleeps(), x, err); > | user_access_end(); > > Calling schedule() without taking an exception doesn't switch the > PSTATE or TTBRs. We can switch out of a uaccess-enabled region, and > run other code with uaccess enabled for a different thread. > > We can also switch from uaccess-disabled code back into this region, > meaning the unsafe_put_user()s will fault. > > For software-PAN, threads that do this will get stuck as > handle_mm_fault() will determine the page has already been mapped in, > but we fault again as the page tables aren't loaded. > > To solve this we need code in __switch_to() that save/restores the > PAN state. > > Signed-off-by: James Morse <james.morse@arm.com> > CC: Julien Thierry <julien.thierry@arm.com> > Acked-by: Mark Rutland <mark.rutland@arm.com> Applied. Thanks.
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h index 8ac6e34922e7..07c34087bd5e 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -276,9 +276,11 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr) : "+r" (err), "=&r" (x) \ : "r" (addr), "i" (-EFAULT)) -#define __get_user_err_unsafe(x, ptr, err) \ +#define __get_user_err(x, ptr, err) \ do { \ unsigned long __gu_val; \ + __chk_user_ptr(ptr); \ + uaccess_enable_not_uao(); \ switch (sizeof(*(ptr))) { \ case 1: \ __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr), \ @@ -299,24 +301,17 @@ do { \ default: \ BUILD_BUG(); \ } \ - (x) = (__force __typeof__(*(ptr)))__gu_val; \ -} while (0) - -#define __get_user_err_check(x, ptr, err) \ -do { \ - __chk_user_ptr(ptr); \ - uaccess_enable_not_uao(); \ - __get_user_err_unsafe((x), (ptr), (err)); \ uaccess_disable_not_uao(); \ + (x) = (__force __typeof__(*(ptr)))__gu_val; \ } while (0) -#define __get_user_err(x, ptr, err, accessor) \ +#define __get_user_check(x, ptr, err) \ ({ \ __typeof__(*(ptr)) __user *__p = (ptr); \ might_fault(); \ if (access_ok(VERIFY_READ, __p, sizeof(*__p))) { \ __p = uaccess_mask_ptr(__p); \ - accessor((x), __p, (err)); \ + __get_user_err((x), __p, (err)); \ } else { \ (x) = 0; (err) = -EFAULT; \ } \ @@ -324,14 +319,14 @@ do { \ #define __get_user_error(x, ptr, err) \ ({ \ - __get_user_err((x), (ptr), (err), __get_user_err_check); \ + __get_user_check((x), (ptr), (err)); \ (void)0; \ }) #define __get_user(x, ptr) \ ({ \ int __gu_err = 0; \ - __get_user_err((x), (ptr), __gu_err, __get_user_err_check); \ + __get_user_check((x), (ptr), __gu_err); \ __gu_err; \ }) @@ -351,9 +346,11 @@ do { \ : "+r" (err) \ : "r" (x), "r" (addr), "i" (-EFAULT)) -#define __put_user_err_unsafe(x, ptr, err) \ +#define __put_user_err(x, ptr, err) \ do { \ __typeof__(*(ptr)) __pu_val = (x); \ + __chk_user_ptr(ptr); \ + uaccess_enable_not_uao(); \ switch (sizeof(*(ptr))) { \ case 1: \ __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr), \ @@ -374,24 +371,16 @@ do { \ default: \ BUILD_BUG(); \ } \ -} while (0) - - -#define __put_user_err_check(x, ptr, err) \ -do { \ - __chk_user_ptr(ptr); \ - uaccess_enable_not_uao(); \ - __put_user_err_unsafe((x), (ptr), (err)); \ uaccess_disable_not_uao(); \ } while (0) -#define __put_user_err(x, ptr, err, accessor) \ +#define __put_user_check(x, ptr, err) \ ({ \ __typeof__(*(ptr)) __user *__p = (ptr); \ might_fault(); \ if (access_ok(VERIFY_WRITE, __p, sizeof(*__p))) { \ __p = uaccess_mask_ptr(__p); \ - accessor((x), __p, (err)); \ + __put_user_err((x), __p, (err)); \ } else { \ (err) = -EFAULT; \ } \ @@ -399,39 +388,19 @@ do { \ #define __put_user_error(x, ptr, err) \ ({ \ - __put_user_err((x), (ptr), (err), __put_user_err_check); \ + __put_user_check((x), (ptr), (err)); \ (void)0; \ }) #define __put_user(x, ptr) \ ({ \ int __pu_err = 0; \ - __put_user_err((x), (ptr), __pu_err, __put_user_err_check); \ + __put_user_check((x), (ptr), __pu_err); \ __pu_err; \ }) #define put_user __put_user - -#define user_access_begin() uaccess_enable_not_uao() -#define user_access_end() uaccess_disable_not_uao() - -#define unsafe_get_user(x, ptr, err) \ -do { \ - int __gu_err = 0; \ - __get_user_err((x), (ptr), __gu_err, __get_user_err_unsafe); \ - if (__gu_err != 0) \ - goto err; \ -} while (0) - -#define unsafe_put_user(x, ptr, err) \ -do { \ - int __pu_err = 0; \ - __put_user_err((x), (ptr), __pu_err, __put_user_err_unsafe); \ - if (__pu_err != 0) \ - goto err; \ -} while (0) - extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n); #define raw_copy_from_user(to, from, n) \ ({ \