Patch "selftests/resctrl: Fix null pointer dereference on open failed" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    selftests/resctrl: Fix null pointer dereference on open failed

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     selftests-resctrl-fix-null-pointer-dereference-on-op.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 0d3035c6fe1efef684c6a55f8a4286e87d4fd7b9
Author: Colin Ian King <colin.king@xxxxxxxxx>
Date:   Tue Apr 26 13:25:31 2022 +0100

    selftests/resctrl: Fix null pointer dereference on open failed
    
    [ Upstream commit c7b607fa9325ccc94982774c505176677117689c ]
    
    Currently if opening /dev/null fails to open then file pointer fp
    is null and further access to fp via fprintf will cause a null
    pointer dereference. Fix this by returning a negative error value
    when a null fp is detected.
    
    Detected using cppcheck static analysis:
    tools/testing/selftests/resctrl/fill_buf.c:124:6: note: Assuming
    that condition '!fp' is not redundant
     if (!fp)
         ^
    tools/testing/selftests/resctrl/fill_buf.c:126:10: note: Null
    pointer dereference
     fprintf(fp, "Sum: %d ", ret);
    
    Fixes: a2561b12fe39 ("selftests/resctrl: Add built in benchmark")
    Signed-off-by: Colin Ian King <colin.i.king@xxxxxxxxx>
    Signed-off-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/tools/testing/selftests/resctrl/fill_buf.c b/tools/testing/selftests/resctrl/fill_buf.c
index 51e5cf22632f..56ccbeae0638 100644
--- a/tools/testing/selftests/resctrl/fill_buf.c
+++ b/tools/testing/selftests/resctrl/fill_buf.c
@@ -121,8 +121,10 @@ static int fill_cache_read(unsigned char *start_ptr, unsigned char *end_ptr,
 
 	/* Consume read result so that reading memory is not optimized out. */
 	fp = fopen("/dev/null", "w");
-	if (!fp)
+	if (!fp) {
 		perror("Unable to write to /dev/null");
+		return -1;
+	}
 	fprintf(fp, "Sum: %d ", ret);
 	fclose(fp);