File avoid-sigbus-on-mmap-failure.patch of Package dmidecode.28672

From: Jean Delvare <jdelvare@suse.de>
Date: Wed, 14 Oct 2015 14:37:04 +0200
Subject: Avoid SIGBUS on mmap failure
Git-commit: c081fa410e7c466df4b3b257e7b974b71fb7f250
Patch-mainline: 3.1

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(+)

--- a/util.c
+++ b/util.c
@@ -155,6 +155,7 @@ 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
@@ -172,6 +173,26 @@ 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