[PATCH] Fix segmentation fault in tailf on 32 bit

[Tobias Stoeckmann <tobias@stoeckmann.org>]

tailf crashes with a segmentation fault when used with a file that is
exactly 4GB in size due to an integer overflow between off_t and size_t:

$ dd if=/dev/zero of=tailf.crash bs=1 count=1 seek=4294967295
$ tailf tailf.crash
Segmentation fault
$ _

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
---
 text-utils/tailf.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/text-utils/tailf.c b/text-utils/tailf.c
index ea082c7..e9ba49b 100644
--- a/text-utils/tailf.c
+++ b/text-utils/tailf.c
@@ -42,6 +42,7 @@
 #include <errno.h>
 #include <getopt.h>
 #include <sys/mman.h>
+#include <limits.h>
 
 #ifdef HAVE_INOTIFY_INIT
 #include <sys/inotify.h>
@@ -55,7 +56,7 @@
 
 #define DEFAULT_LINES  10
 
-/* st->st_size has to be greater than zero! */
+/* st->st_size has to be greater than zero and smaller or equal to SIZE_MAX! */
 static void tailf(const char *filename, size_t lines, struct stat *st)
 {
 	int fd;
@@ -281,7 +282,7 @@ int main(int argc, char **argv)
 		err(EXIT_FAILURE, _("stat of %s failed"), filename);
 	if (!S_ISREG(st.st_mode))
 		errx(EXIT_FAILURE, _("%s: is not a file"), filename);
-	if (st.st_size)
+	if (st.st_size && st.st_size <= SIZE_MAX)
 		tailf(filename, lines, &st);
 
 #ifdef HAVE_INOTIFY_INIT
-- 
2.9.0