vsprintf: Fix potential unaligned access

[ Upstream commit d75b26f880f60ead301e79ba0f4a635c5a60767f ]

The %p4cc specifier in some cases might get an unaligned pointer.
Due to this we need to make copy to local variable once to avoid
potential crashes on some architectures due to improper access.

Fixes: af612e43de6d ("lib/vsprintf: Add support for printing V4L2 and DRM fourccs")
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20220127181233.72910-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 3b8129dd374cd96f66439a826983e2bcc63cce70..1ff73ac9e820f15791e8a2517a18b3d83030a4f1 100644 (file)
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -49,6 +49,7 @@
 
 #include <asm/page.h>          /* for PAGE_SIZE */
 #include <asm/byteorder.h>     /* cpu_to_le16 */
+#include <asm/unaligned.h>
 
 #include <linux/string_helpers.h>
 #include "kstrtox.h"
@@ -1761,7 +1762,7 @@ char *fourcc_string(char *buf, char *end, const u32 *fourcc,
        char output[sizeof("0123 little-endian (0x01234567)")];
        char *p = output;
        unsigned int i;
-       u32 val;
+       u32 orig, val;
 
        if (fmt[1] != 'c' || fmt[2] != 'c')
                return error_string(buf, end, "(%p4?)", spec);
@@ -1769,21 +1770,22 @@ char *fourcc_string(char *buf, char *end, const u32 *fourcc,
        if (check_pointer(&buf, end, fourcc, spec))
                return buf;
 
-       val = *fourcc & ~BIT(31);
+       orig = get_unaligned(fourcc);
+       val = orig & ~BIT(31);
 
-       for (i = 0; i < sizeof(*fourcc); i++) {
+       for (i = 0; i < sizeof(u32); i++) {
                unsigned char c = val >> (i * 8);
 
                /* Print non-control ASCII characters as-is, dot otherwise */
                *p++ = isascii(c) && isprint(c) ? c : '.';
        }
 
-       strcpy(p, *fourcc & BIT(31) ? " big-endian" : " little-endian");
+       strcpy(p, orig & BIT(31) ? " big-endian" : " little-endian");
        p += strlen(p);
 
        *p++ = ' ';
        *p++ = '(';
-       p = special_hex_number(p, output + sizeof(output) - 2, *fourcc, sizeof(u32));
+       p = special_hex_number(p, output + sizeof(output) - 2, orig, sizeof(u32));
        *p++ = ')';
        *p = '\0';