tools: mkimage: Ensure munmap unmaps the same length that was mapped

The set_header call in kwbimage.c adds a checksum to the end of the
image in addition to setting up the header. It 'helpfully' updates the
st_size to match the fact that the file is now longer. However, mkimage
uses this length in the munmap call. This can lead to unmapping an extra
page, of perhaps required data. When this happens, a SEGV can occur.

To prevent this from happening, the munmap call now uses the same length
that was passed to mmap. This could also have been fixed by not changing
the length in kwbimage.c, however changing it in the main file means
that other plugins will also not fall for the same trap.

Signed-off-by: Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz>
Signed-off-by: Chris Packham <judge.packham@gmail.com>
[cp: resolve checkpatch complaints]
Tested-by: Chris Packham <judge.packham@gmail.com>

diff --git a/tools/mkimage.c b/tools/mkimage.c
index e0d4d20be499cd1e869466e9594269034251fba9..6abd4d6a8b2210984cd49fb510118b9d300dfe22 100644 (file)
--- a/tools/mkimage.c
+++ b/tools/mkimage.c
@@ -318,6 +318,7 @@ int main(int argc, char **argv)
        struct image_type_params *tparams = NULL;
        int pad_len = 0;
        int dfd;
+       size_t map_len;
 
        params.cmdname = *argv;
        params.addr = 0;
@@ -576,7 +577,8 @@ int main(int argc, char **argv)
        }
        params.file_size = sbuf.st_size;
 
-       ptr = mmap(0, sbuf.st_size, PROT_READ|PROT_WRITE, MAP_SHARED, ifd, 0);
+       map_len = sbuf.st_size;
+       ptr = mmap(0, map_len, PROT_READ | PROT_WRITE, MAP_SHARED, ifd, 0);
        if (ptr == MAP_FAILED) {
                fprintf (stderr, "%s: Can't map %s: %s\n",
                        params.cmdname, params.imagefile, strerror(errno));
@@ -600,7 +602,7 @@ int main(int argc, char **argv)
                        params.cmdname, tparams->name);
        }
 
-       (void) munmap((void *)ptr, sbuf.st_size);
+       (void)munmap((void *)ptr, map_len);
 
        /* We're a bit of paranoid */
 #if defined(_POSIX_SYNCHRONIZED_IO) && \