Avoid SIGBUS on mmap failure

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
somarasa · Oct 14, 2015 · c081fa4 · c081fa4
1 parent 33b5aaf
commit c081fa4
Show file tree

Hide file tree

Showing 2 changed files with 27 additions and 0 deletions.
diff --git a/CHANGELOG b/CHANGELOG
@@ -1,3 +1,9 @@
+2015-10-14  Jean Delvare  <jdelvare@suse.de>
+
+	* util.c: Avoid SIGBUS on mmap failure.
+	  This fixes Savannah bug #46066:
+	  https://savannah.nongnu.org/bugs/?46066
+
 2015-10-01  Roy Franz  <roy.franz@linaro.org>
 
 	* dmiopt.c: Add "--no-sysfs" option description to -h output.

diff --git a/util.c b/util.c
@@ -152,6 +152,7 @@ void *mem_chunk(off_t base, size_t len, const char *devmem)
 	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, const char *devmem)
 	}
 
 #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