The following if (val < 0) *lvalp = (unsigned long)-val;
is incorrect because the compiler is free to assume -val to be positive and use a sign-extend instruction for extending the bit pattern. This is a problem if val == INT_MIN: # echo -2147483648 >/proc/sys/dev/scsi/logging_level # cat /proc/sys/dev/scsi/logging_level -18446744071562067968 Cast to unsigned long before negation - that way we first sign-extend and then negate an unsigned, which is well defined. With this: # cat /proc/sys/dev/scsi/logging_level -2147483648 Signed-off-by: Ilya Dryomov <idryo...@gmail.com> --- kernel/sysctl.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 19b62b522158..0b4092b9fa00 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1995,7 +1995,7 @@ static int do_proc_dointvec_conv(bool *negp, unsigned long *lvalp, int val = *valp; if (val < 0) { *negp = true; - *lvalp = (unsigned long)-val; + *lvalp = -(unsigned long)val; } else { *negp = false; *lvalp = (unsigned long)val; @@ -2201,7 +2201,7 @@ static int do_proc_dointvec_minmax_conv(bool *negp, unsigned long *lvalp, int val = *valp; if (val < 0) { *negp = true; - *lvalp = (unsigned long)-val; + *lvalp = -(unsigned long)val; } else { *negp = false; *lvalp = (unsigned long)val; @@ -2436,7 +2436,7 @@ static int do_proc_dointvec_jiffies_conv(bool *negp, unsigned long *lvalp, unsigned long lval; if (val < 0) { *negp = true; - lval = (unsigned long)-val; + lval = -(unsigned long)val; } else { *negp = false; lval = (unsigned long)val; @@ -2459,7 +2459,7 @@ static int do_proc_dointvec_userhz_jiffies_conv(bool *negp, unsigned long *lvalp unsigned long lval; if (val < 0) { *negp = true; - lval = (unsigned long)-val; + lval = -(unsigned long)val; } else { *negp = false; lval = (unsigned long)val; @@ -2484,7 +2484,7 @@ static int do_proc_dointvec_ms_jiffies_conv(bool *negp, unsigned long *lvalp, unsigned long lval; if (val < 0) { *negp = true; - lval = (unsigned long)-val; + lval = -(unsigned long)val; } else { *negp = false; lval = (unsigned long)val; -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/