Re: [PATCH] vboxsf: fix comparison of signed char constant with unsigned char array elements

From: Hans de Goede
Date: Wed Sep 16 2020 - 02:14:30 EST


Hi,

On 9/15/20 6:03 PM, Colin King wrote:
From: Colin Ian King <colin.king@xxxxxxxxxxxxx>

The comparison of signed char constants with unsigned char array
elements leads to checks that are always false. Fix this by declaring
the VBSF_MOUNT_SIGNATURE_BYTE* macros as octal unsigned int constants
rather than as signed char constants. (Argueably the U is not necessarily
required, but add it to be really clear of intent).

Addresses-Coverity: ("Operands don't affect result")
Fixes: 0fd169576648 ("fs: Add VirtualBox guest shared folder (vboxsf) support")
Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>

A fix for this has already been queued up:

https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git/log/?h=fixes

Explicit nack for this one, since it will still apply, but combined
with the other fix, it will re-break things.

Regards,

Hans



---
fs/vboxsf/super.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/vboxsf/super.c b/fs/vboxsf/super.c
index 25aade344192..986efcb29cc2 100644
--- a/fs/vboxsf/super.c
+++ b/fs/vboxsf/super.c
@@ -21,10 +21,10 @@
#define VBOXSF_SUPER_MAGIC 0x786f4256 /* 'VBox' little endian */
-#define VBSF_MOUNT_SIGNATURE_BYTE_0 ('\000')
-#define VBSF_MOUNT_SIGNATURE_BYTE_1 ('\377')
-#define VBSF_MOUNT_SIGNATURE_BYTE_2 ('\376')
-#define VBSF_MOUNT_SIGNATURE_BYTE_3 ('\375')
+#define VBSF_MOUNT_SIGNATURE_BYTE_0 0000U
+#define VBSF_MOUNT_SIGNATURE_BYTE_1 0377U
+#define VBSF_MOUNT_SIGNATURE_BYTE_2 0376U
+#define VBSF_MOUNT_SIGNATURE_BYTE_3 0375U
static int follow_symlinks;
module_param(follow_symlinks, int, 0444);