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kernel/sys.c:1287:10: warning: comparison of distinct pointer types lacks a cast

PATCH In review Fengguang Wu 2 participants 3 messages Oct 12, 2012 Kernel janitors

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Fengguang Wu

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#0 lore raw

PATCH 18/86 kernel/sys.c:1287:10: warning: comparison of distinct pointer types lacks a cast

Hi Kees,

FYI, there are new compile warnings show up in

tree:   git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git akpm
head:   04b956faad392f46c9a234962a9990196b8e48fc
commit: b8763455880e371a81b07599bc66ae94f96dc6d6 [18/86] kernel/sys.c: fix stack memory content leak via UNAME26
config: mn10300-asb2364_defconfig # make ARCH=mn10300 asb2364_defconfig

All warnings:

kernel/sys.c: In function 'override_release':
kernel/sys.c:1287:10: warning: comparison of distinct pointer types lacks a cast [enabled by default]

vim +1287 kernel/sys.c

be27425d Andi Kleen     2011-08-19  1271  
be27425d Andi Kleen     2011-08-19  1272  	if (current->personality & UNAME26) {
b8763455 Kees Cook      2012-10-12  1273  		const char *rest = UTS_RELEASE;
b8763455 Kees Cook      2012-10-12  1274  		char buf[65] = { 0 };
be27425d Andi Kleen     2011-08-19  1275  		int ndots = 0;
be27425d Andi Kleen     2011-08-19  1276  		unsigned v;
b8763455 Kees Cook      2012-10-12  1277  		size_t copy;
be27425d Andi Kleen     2011-08-19  1278  
be27425d Andi Kleen     2011-08-19  1279  		while (*rest) {
be27425d Andi Kleen     2011-08-19  1280  			if (*rest = '.' && ++ndots >= 3)
be27425d Andi Kleen     2011-08-19  1281  				break;
be27425d Andi Kleen     2011-08-19  1282  			if (!isdigit(*rest) && *rest != '.')
be27425d Andi Kleen     2011-08-19  1283  				break;
be27425d Andi Kleen     2011-08-19  1284  			rest++;
be27425d Andi Kleen     2011-08-19  1285  		}
be27425d Andi Kleen     2011-08-19  1286  		v = ((LINUX_VERSION_CODE >> 8) & 0xff) + 40;
b8763455 Kees Cook      2012-10-12 @1287  		copy = min(sizeof(buf), max_t(size_t, 1, len));
b8763455 Kees Cook      2012-10-12  1288  		copy = scnprintf(buf, copy, "2.6.%u%s", v, rest);
b8763455 Kees Cook      2012-10-12  1289  		ret = copy_to_user(release, buf, copy + 1);
be27425d Andi Kleen     2011-08-19  1290  	}
be27425d Andi Kleen     2011-08-19  1291  	return ret;
be27425d Andi Kleen     2011-08-19  1292  }
be27425d Andi Kleen     2011-08-19  1293  
e48fbb69 Heiko Carstens 2009-01-14  1294  SYSCALL_DEFINE1(newuname, struct new_utsname __user *, name)
^1da177e Linus Torvalds 2005-04-16  1295  {

---
0-DAY kernel build testing backend Open Source Technology Center
Fengguang Wu, Yuanhan Liu Intel Corporation

#1 lore raw

Re: [next:akpm 18/86] kernel/sys.c:1287:10: warning: comparison of distinct pointer types lacks a ca

Quoted 11 lines · Fengguang Wu

FYI, there are new compile warnings show up in

tree:   git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git akpm
head:   04b956faad392f46c9a234962a9990196b8e48fc
commit: b8763455880e371a81b07599bc66ae94f96dc6d6 [18/86] kernel/sys.c: fix stack memory content leak via UNAME26
config: mn10300-asb2364_defconfig # make ARCH=mn10300 asb2364_defconfig

All warnings:

kernel/sys.c: In function 'override_release':
kernel/sys.c:1287:10: warning: comparison of distinct pointer types lacks a cast [enabled by default]

Hrm, I don't see this on my builds. Is this check specific to mn10300 in some way?

Quoted 11 lines

vim +1287 kernel/sys.c

be27425d Andi Kleen     2011-08-19  1271
be27425d Andi Kleen     2011-08-19  1272        if (current->personality & UNAME26) {
b8763455 Kees Cook      2012-10-12  1273                const char *rest = UTS_RELEASE;
b8763455 Kees Cook      2012-10-12  1274                char buf[65] = { 0 };
be27425d Andi Kleen     2011-08-19  1275                int ndots = 0;
be27425d Andi Kleen     2011-08-19  1276                unsigned v;
b8763455 Kees Cook      2012-10-12  1277                size_t copy;
be27425d Andi Kleen     2011-08-19  1278
be27425d Andi Kleen     2011-08-19  1279                while (*rest) {
Quoted 8 lines
be27425d Andi Kleen     2011-08-19  1280                        if (*rest = '.' && ++ndots >= 3)
be27425d Andi Kleen     2011-08-19  1281                                break;
be27425d Andi Kleen     2011-08-19  1282                        if (!isdigit(*rest) && *rest != '.')
be27425d Andi Kleen     2011-08-19  1283                                break;
be27425d Andi Kleen     2011-08-19  1284                        rest++;
be27425d Andi Kleen     2011-08-19  1285                }
be27425d Andi Kleen     2011-08-19  1286                v = ((LINUX_VERSION_CODE >> 8) & 0xff) + 40;
b8763455 Kees Cook      2012-10-12 @1287                copy = min(sizeof(buf), max_t(size_t, 1, len));

Should I change this to min_t(size_t, sizeof(buf), max_t(size_t, 1, len)) ?

Thanks!

-Kees

Signature · 2 lines
Kees Cook
Chrome OS Security
author
#2 lore raw

Re: [next:akpm 18/86] kernel/sys.c:1287:10: warning: comparison of distinct pointer types lacks a ca

In reply to Fengguang Wu
Quoted 8 lines · Kees Cook
Quoted 7 lines · Fengguang Wu

FYI, there are new compile warnings show up in

tree:   git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git akpm
head:   04b956faad392f46c9a234962a9990196b8e48fc
commit: b8763455880e371a81b07599bc66ae94f96dc6d6 [18/86] kernel/sys.c: fix stack memory content leak via UNAME26
config: mn10300-asb2364_defconfig # make ARCH=mn10300 asb2364_defconfig
Quoted 7 lines
Quoted 4 lines

All warnings:

kernel/sys.c: In function 'override_release':
kernel/sys.c:1287:10: warning: comparison of distinct pointer types lacks a cast [enabled by default]

Hrm, I don't see this on my builds. Is this check specific to mn10300 in some way?

Maybe it's more than mn10300.

(gdb) whatis sizeof(long)
type = int

And size_t (__kernel_size_t) is defined to "unsigned int".

Quoted 20 lines
Quoted 11 lines

vim +1287 kernel/sys.c

be27425d Andi Kleen     2011-08-19  1271
be27425d Andi Kleen     2011-08-19  1272        if (current->personality & UNAME26) {
b8763455 Kees Cook      2012-10-12  1273                const char *rest = UTS_RELEASE;
b8763455 Kees Cook      2012-10-12  1274                char buf[65] = { 0 };
be27425d Andi Kleen     2011-08-19  1275                int ndots = 0;
be27425d Andi Kleen     2011-08-19  1276                unsigned v;
b8763455 Kees Cook      2012-10-12  1277                size_t copy;
be27425d Andi Kleen     2011-08-19  1278
be27425d Andi Kleen     2011-08-19  1279                while (*rest) {
Quoted 8 lines
be27425d Andi Kleen     2011-08-19  1280                        if (*rest = '.' && ++ndots >= 3)
be27425d Andi Kleen     2011-08-19  1281                                break;
be27425d Andi Kleen     2011-08-19  1282                        if (!isdigit(*rest) && *rest != '.')
be27425d Andi Kleen     2011-08-19  1283                                break;
be27425d Andi Kleen     2011-08-19  1284                        rest++;
be27425d Andi Kleen     2011-08-19  1285                }
be27425d Andi Kleen     2011-08-19  1286                v = ((LINUX_VERSION_CODE >> 8) & 0xff) + 40;
b8763455 Kees Cook      2012-10-12 @1287                copy = min(sizeof(buf), max_t(size_t, 1, len));
Quoted 1 line

Should I change this to min_t(size_t, sizeof(buf), max_t(size_t, 1, len)) ?

clamp_t() looks easier. :-)

Thanks,
Fengguang