[dmidecode] [PATCH 1/2] Avoid SIGBUS on mmap failure

[Jean Delvare]

mmap will fail with SIGBUS if trying to map a non-existent portion of
a file. While this should never happen with /dev/mem, it can happen if
passing a regular file with option -d. While people should no longer
do that, failure gracefully seems better than crashing. So check for
the file size before calling mmap.

This closes bug #46066:
http://savannah.nongnu.org/bugs/?46066
---
 util.c |   21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

--- dmidecode.orig/util.c       2015-09-29 11:27:02.136566009 +0200
+++ dmidecode/util.c    2015-09-29 11:37:24.746191083 +0200
@@ -152,6 +152,7 @@ void *mem_chunk(off_t base, size_t len,
        void *p;
        int fd;
 #ifdef USE_MMAP
+       struct stat statbuf;
        off_t mmoffset;
        void *mmp;
 #endif
@@ -169,6 +170,26 @@ void *mem_chunk(off_t base, size_t len,
        }
 
 #ifdef USE_MMAP
+       if (fstat(fd, &statbuf) == -1)
+       {
+               fprintf(stderr, "%s: ", devmem);
+               perror("stat");
+               free(p);
+               return NULL;
+       }
+
+       /*
+        * mmap() will fail with SIGBUS if trying to map beyond the end of
+        * the file.
+        */
+       if (S_ISREG(statbuf.st_mode) && base + (off_t)len > statbuf.st_size)
+       {
+               fprintf(stderr, "mmap: Can't map beyond end of file %s\n",
+                       devmem);
+               free(p);
+               return NULL;
+       }
+
 #ifdef _SC_PAGESIZE
        mmoffset = base % sysconf(_SC_PAGESIZE);
 #else


-- 
Jean Delvare
SUSE L3 Support