| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.10 052/110] s390/uaccess: get_user() should zero on failure (again) | Date | Mon, 10 Apr 2017 18:42:43 +0200 |
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4.10-stable review patch. If anyone has any objections, please let me know.
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From: Heiko Carstens <heiko.carstens@de.ibm.com>
commit d09c5373e8e4eaaa09233552cbf75dc4c4f21203 upstream.
Commit fd2d2b191fe7 ("s390: get_user() should zero on failure") intended to fix s390's get_user() implementation which did not zero the target operand if the read from user space faulted. Unfortunately the patch has no effect: the corresponding inline assembly specifies that the operand is only written to ("=") and the previous value is discarded.
Therefore the compiler is free to and actually does omit the zero initialization.
To fix this simply change the contraint modifier to "+", so the compiler cannot omit the initialization anymore.
Fixes: c9ca78415ac1 ("s390/uaccess: provide inline variants of get_user/put_user") Fixes: fd2d2b191fe7 ("s390: get_user() should zero on failure") Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- arch/s390/include/asm/uaccess.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/s390/include/asm/uaccess.h +++ b/arch/s390/include/asm/uaccess.h @@ -144,7 +144,7 @@ unsigned long __must_check __copy_to_use " jg 2b\n" \ ".popsection\n" \ EX_TABLE(0b,3b) EX_TABLE(1b,3b) \ - : "=d" (__rc), "=Q" (*(to)) \ + : "=d" (__rc), "+Q" (*(to)) \ : "d" (size), "Q" (*(from)), \ "d" (__reg0), "K" (-EFAULT) \ : "cc"); \
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