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sysctl: fix int -> unsigned long assignments in INT_MIN case

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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 <idryomov@gmail.com>
Cc: Mikulas Patocka <mikulas@twibright.com>
Cc: Robert Xiao <nneonneo@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Ilya Dryomov 2015-09-09 15:39:06 -07:00 committed by Linus Torvalds
parent 1303a27c9c
commit 9a5bc726d5
1 changed files with 5 additions and 5 deletions
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10
kernel/sysctl.c
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@ -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;