4.18-stable review patch. If anyone has any objections, please let me know.
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From: Michael Ellerman mpe@ellerman.id.au
[ Upstream commit f7a6947cd49b7ff4e03f1b4f7e7b223003d752ca ]
Currently if you build a 32-bit powerpc kernel and use get_user() to load a u64 value it will fail to build with eg:
kernel/rseq.o: In function `rseq_get_rseq_cs': kernel/rseq.c:123: undefined reference to `__get_user_bad'
This is hitting the check in __get_user_size() that makes sure the size we're copying doesn't exceed the size of the destination:
#define __get_user_size(x, ptr, size, retval) do { retval = 0; __chk_user_ptr(ptr); if (size > sizeof(x)) (x) = __get_user_bad();
Which doesn't immediately make sense because the size of the destination is u64, but it's not really, because __get_user_check() etc. internally create an unsigned long and copy into that:
#define __get_user_check(x, ptr, size) ({ long __gu_err = -EFAULT; unsigned long __gu_val = 0;
The problem being that on 32-bit unsigned long is not big enough to hold a u64. We can fix this with a trick from hpa in the x86 code, we statically check the type of x and set the type of __gu_val to either unsigned long or unsigned long long.
Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/include/asm/uaccess.h | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)
--- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -250,10 +250,17 @@ do { \ } \ } while (0)
+/* + * This is a type: either unsigned long, if the argument fits into + * that type, or otherwise unsigned long long. + */ +#define __long_type(x) \ + __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL)) + #define __get_user_nocheck(x, ptr, size) \ ({ \ long __gu_err; \ - unsigned long __gu_val; \ + __long_type(*(ptr)) __gu_val; \ const __typeof__(*(ptr)) __user *__gu_addr = (ptr); \ __chk_user_ptr(ptr); \ if (!is_kernel_addr((unsigned long)__gu_addr)) \ @@ -267,7 +274,7 @@ do { \ #define __get_user_check(x, ptr, size) \ ({ \ long __gu_err = -EFAULT; \ - unsigned long __gu_val = 0; \ + __long_type(*(ptr)) __gu_val = 0; \ const __typeof__(*(ptr)) __user *__gu_addr = (ptr); \ might_fault(); \ if (access_ok(VERIFY_READ, __gu_addr, (size))) { \ @@ -281,7 +288,7 @@ do { \ #define __get_user_nosleep(x, ptr, size) \ ({ \ long __gu_err; \ - unsigned long __gu_val; \ + __long_type(*(ptr)) __gu_val; \ const __typeof__(*(ptr)) __user *__gu_addr = (ptr); \ __chk_user_ptr(ptr); \ barrier_nospec(); \