[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[PATCH v2 1/3] vsscanf(): Integer overflow is a conversion failure



sscanf() and friends currently ignore integer overflow, but this is a
bad idea.  It is much better to detect integer overflow errors and
consider this a conversion failure.

This implements Linus's suggestion of using '!' to treat integer
overflow as wrapping.  It does _not_ allow wrapping of unsigned
conversions by default, though, as in at least some cases accepting
negative numbers is _not_ intended.

Suggested-By: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
---
 .../hive_isp_css_include/platform_support.h   |  1 -
 include/linux/limits.h                        |  1 +
 include/linux/mfd/wl1273-core.h               |  3 -
 include/vdso/limits.h                         |  3 +
 lib/vsprintf.c                                | 82 ++++++++++++++-----
 5 files changed, 67 insertions(+), 23 deletions(-)

diff --git 
a/drivers/staging/media/atomisp/pci/hive_isp_css_include/platform_support.h 
b/drivers/staging/media/atomisp/pci/hive_isp_css_include/platform_support.h
index 
0cdef4a5e8b1bed9884133f1a0b9d853d59d43a4..e29b96d8bebf14839f6dd48fdc6c0f8b029ef31d
 100644
--- a/drivers/staging/media/atomisp/pci/hive_isp_css_include/platform_support.h
+++ b/drivers/staging/media/atomisp/pci/hive_isp_css_include/platform_support.h
@@ -27,7 +27,6 @@
 
 #define UINT16_MAX USHRT_MAX
 #define UINT32_MAX UINT_MAX
-#define UCHAR_MAX  (255)
 
 #define CSS_ALIGN(d, a) d __attribute__((aligned(a)))
 
diff --git a/include/linux/limits.h b/include/linux/limits.h
index 
f6bcc936901071f496e3e85bb6e1d93905b12e32..8f7fd85b41fb46e6992d9e5912da00424119227a
 100644
--- a/include/linux/limits.h
+++ b/include/linux/limits.h
@@ -8,6 +8,7 @@
 
 #define SIZE_MAX       (~(size_t)0)
 #define SSIZE_MAX      ((ssize_t)(SIZE_MAX >> 1))
+#define SSIZE_MIN      (-SSIZE_MAX - 1)
 #define PHYS_ADDR_MAX  (~(phys_addr_t)0)
 
 #define U8_MAX         ((u8)~0U)
diff --git a/include/linux/mfd/wl1273-core.h b/include/linux/mfd/wl1273-core.h
index 
c28cf76d5c31ee1c94a9319a2e2d318bf00283a6..b81a229135ed9f756c749122a8341816031c8311
 100644
--- a/include/linux/mfd/wl1273-core.h
+++ b/include/linux/mfd/wl1273-core.h
@@ -204,9 +204,6 @@
                                 WL1273_IS2_TRI_OPT | \
                                 WL1273_IS2_RATE_48K)
 
-#define SCHAR_MIN (-128)
-#define SCHAR_MAX 127
-
 #define WL1273_FR_EVENT                        BIT(0)
 #define WL1273_BL_EVENT                        BIT(1)
 #define WL1273_RDS_EVENT               BIT(2)
diff --git a/include/vdso/limits.h b/include/vdso/limits.h
index 
0197888ad0e00b2f853d3f25ffa764f61cca7385..0cad0a2490e5efc194d874025eb3e3b846a5c7b4
 100644
--- a/include/vdso/limits.h
+++ b/include/vdso/limits.h
@@ -2,6 +2,9 @@
 #ifndef __VDSO_LIMITS_H
 #define __VDSO_LIMITS_H
 
+#define UCHAR_MAX      ((unsigned char)~0U)
+#define SCHAR_MAX      ((signed char)(UCHAR_MAX >> 1))
+#define SCHAR_MIN      ((signed char)(-SCHAR_MAX - 1))
 #define USHRT_MAX      ((unsigned short)~0U)
 #define SHRT_MAX       ((short)(USHRT_MAX >> 1))
 #define SHRT_MIN       ((short)(-SHRT_MAX - 1))
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 
40f560959b169b4c4ac6154d658cfe76cfd0c5a6..8caccdcda0a2b470cda70c9b3837de37207eb512
 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -59,7 +59,7 @@
 bool no_hash_pointers __ro_after_init;
 EXPORT_SYMBOL_GPL(no_hash_pointers);
 
-static noinline unsigned long long simple_strntoull(const char *startp, size_t 
max_chars, char **endp, unsigned int base)
+static noinline unsigned long long simple_strntoull(const char *startp, size_t 
max_chars, char **endp, unsigned int base, bool *overflow)
 {
        const char *cp;
        unsigned long long result = 0ULL;
@@ -71,6 +71,8 @@ static noinline unsigned long long simple_strntoull(const 
char *startp, size_t m
        if (prefix_chars < max_chars) {
                rv = _parse_integer_limit(cp, base, &result, max_chars - 
prefix_chars);
                /* FIXME */
+               if (overflow)
+                       *overflow = !!(rv & KSTRTOX_OVERFLOW);
                cp += (rv & ~KSTRTOX_OVERFLOW);
        } else {
                /* Field too short for prefix + digit, skip over without 
converting */
@@ -94,7 +96,7 @@ static noinline unsigned long long simple_strntoull(const 
char *startp, size_t m
 noinline
 unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int 
base)
 {
-       return simple_strntoull(cp, INT_MAX, endp, base);
+       return simple_strntoull(cp, INT_MAX, endp, base, NULL);
 }
 EXPORT_SYMBOL(simple_strtoull);
 
@@ -130,18 +132,22 @@ long simple_strtol(const char *cp, char **endp, unsigned 
int base)
 EXPORT_SYMBOL(simple_strtol);
 
 static long long simple_strntoll(const char *cp, size_t max_chars, char **endp,
-                                unsigned int base)
+                                unsigned int base, bool *overflow)
 {
+       unsigned long long minand;
+       bool negate;
+
        /*
         * simple_strntoull() safely handles receiving max_chars==0 in the
         * case cp[0] == '-' && max_chars == 1.
         * If max_chars == 0 we can drop through and pass it to 
simple_strntoull()
         * and the content of *cp is irrelevant.
         */
-       if (*cp == '-' && max_chars > 0)
-               return -simple_strntoull(cp + 1, max_chars - 1, endp, base);
-
-       return simple_strntoull(cp, max_chars, endp, base);
+       negate = *cp == '-' && max_chars > 0;
+       minand = simple_strntoull(cp + negate, max_chars - negate, endp, base, 
overflow);
+       if (minand > (unsigned long long)LONG_MAX + negate)
+               *overflow = true;
+       return negate ? -minand : minand;
 }
 
 /**
@@ -3441,7 +3447,7 @@ int vsscanf(const char *buf, const char *fmt, va_list 
args)
                unsigned long long u;
        } val;
        s16 field_width;
-       bool is_sign;
+       bool is_sign, overflow, allow_overflow;
 
        while (*fmt) {
                /* skip any white space in format */
@@ -3464,6 +3470,9 @@ int vsscanf(const char *buf, const char *fmt, va_list 
args)
                        break;
                ++fmt;
 
+               allow_overflow = *fmt == '!';
+               fmt += (int)allow_overflow;
+
                /* skip this conversion.
                 * advance both strings to next white space
                 */
@@ -3649,45 +3658,80 @@ int vsscanf(const char *buf, const char *fmt, va_list 
args)
                if (is_sign)
                        val.s = simple_strntoll(str,
                                                field_width >= 0 ? field_width 
: INT_MAX,
-                                               &next, base);
+                                               &next, base, &overflow);
                else
                        val.u = simple_strntoull(str,
                                                 field_width >= 0 ? field_width 
: INT_MAX,
-                                                &next, base);
+                                                &next, base, &overflow);
+               if (unlikely(overflow && !allow_overflow))
+                       break;
 
                switch (qualifier) {
                case 'H':       /* that's 'hh' in format */
-                       if (is_sign)
+                       if (is_sign) {
+                               if (unlikely(val.s < SCHAR_MIN || val.s > 
SCHAR_MAX) &&
+                                   !allow_overflow)
+                                       return num;
                                *va_arg(args, signed char *) = val.s;
-                       else
+                       } else {
+                               if (unlikely(val.u > UCHAR_MAX) && 
!allow_overflow)
+                                       return num;
                                *va_arg(args, unsigned char *) = val.u;
+                       }
                        break;
                case 'h':
-                       if (is_sign)
+                       if (is_sign) {
+                               if (unlikely(val.s < SHRT_MIN || val.s > 
SHRT_MAX) &&
+                                   !allow_overflow)
+                                       return num;
                                *va_arg(args, short *) = val.s;
-                       else
+                       } else {
+                               if (unlikely(val.u > USHRT_MAX) && 
!allow_overflow)
+                                       return num;
                                *va_arg(args, unsigned short *) = val.u;
+                       }
                        break;
                case 'l':
-                       if (is_sign)
+                       if (is_sign) {
+                               if (unlikely(val.s < LONG_MIN || val.s > 
LONG_MAX) &&
+                                   !allow_overflow)
+                                       return num;
                                *va_arg(args, long *) = val.s;
-                       else
+                       } else {
+                               if (unlikely(val.u > ULONG_MAX) && 
!allow_overflow)
+                                       return num;
                                *va_arg(args, unsigned long *) = val.u;
+                       }
                        break;
                case 'L':
+                       /* No overflow check needed */
                        if (is_sign)
                                *va_arg(args, long long *) = val.s;
                        else
                                *va_arg(args, unsigned long long *) = val.u;
                        break;
                case 'z':
-                       *va_arg(args, size_t *) = val.u;
+                       if (is_sign) {
+                               if (unlikely(val.s < SSIZE_MIN || val.s > 
SSIZE_MAX))
+                                       return num;
+                               *va_arg(args, ssize_t *) = val.s;
+                       } else {
+                               if (unlikely(val.u > SIZE_MAX) && 
!allow_overflow)
+                                       return num;
+                               *va_arg(args, size_t *) = val.u;
+                       }
                        break;
                default:
-                       if (is_sign)
+                       if (is_sign) {
+                               if (unlikely(val.s < INT_MIN || val.s > 
INT_MAX) &&
+                                   !allow_overflow)
+                                       return num;
                                *va_arg(args, int *) = val.s;
-                       else
+                       } else {
+                               if (unlikely(val.u > UINT_MAX) && 
!allow_overflow)
+                                       return num;
                                *va_arg(args, unsigned int *) = val.u;
+                       }
                        break;
                }
                num++;
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab




 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.