[PATCH 3.16.y-ckt 122/133] perf/x86: Fix copy_from_user_nmi() return if range is not ok

Luis Henriques luis.henriques at canonical.com
Wed Sep 30 09:51:10 UTC 2015


3.16.7-ckt18 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Yann Droneaud <ydroneaud at opteya.com>

commit ebf2d2689de551d90965090bb991fc640a0c0d41 upstream.

Commit 0a196848ca36 ("perf: Fix arch_perf_out_copy_user default"),
changes copy_from_user_nmi() to return the number of
remaining bytes so that it behave like copy_from_user().

Unfortunately, when the range is outside of the process
memory, the return value  is still the number of byte
copied, eg. 0, instead of the remaining bytes.

As all users of copy_from_user_nmi() were modified as
part of commit 0a196848ca36, the function should be
fixed to return the total number of bytes if range is
not correct.

Signed-off-by: Yann Droneaud <ydroneaud at opteya.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Link: http://lkml.kernel.org/r/1435001923-30986-1-git-send-email-ydroneaud@opteya.com
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Cc: Yann Droneaud <ydroneaud at opteya.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/x86/lib/usercopy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c
index ddf9ecb53cc3..e342586db6e4 100644
--- a/arch/x86/lib/usercopy.c
+++ b/arch/x86/lib/usercopy.c
@@ -20,7 +20,7 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
 	unsigned long ret;
 
 	if (__range_not_ok(from, n, TASK_SIZE))
-		return 0;
+		return n;
 
 	/*
 	 * Even though this function is typically called from NMI/IRQ context




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