lkml.org 
[lkml]   [2016]   [Nov]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2] time: Avoid signed overflow in timekeeping_delta_to_ns()
Date
This bug was originally fixed in commit 35a4933a8959 ("time:
Avoid signed overflow in timekeeping_get_ns()"). When the code was
refactored in commit 6bd58f09e1d8 ("time: Add cycles to nanoseconds
translation") the signed overflow fix was lost. Re-introduce it
in a less subtle way by changing the type of "nsec" to unsigned
and adding a comment explaining why.

Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
---
v2: just use "u64 nsec" to fix the signed shift problem

kernel/time/timekeeping.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 37dec7e3db43..8c06a2aa9b5f 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -302,7 +302,7 @@ static inline u32 arch_gettimeoffset(void) { return 0; }
static inline s64 timekeeping_delta_to_ns(struct tk_read_base *tkr,
cycle_t delta)
{
- s64 nsec;
+ u64 nsec; /* Avoid possibility of a negative right shift. */

nsec = delta * tkr->mult + tkr->xtime_nsec;
nsec >>= tkr->shift;
--
2.7.2
\
 
 \ /
  Last update: 2016-11-16 22:20    [W:1.190 / U:0.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site