linux-kernel - Re: [PATCH][next] staging: gpib: fix unset padding field copy back to userspace

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Message-ID: <30c88178-173e-4432-ab2f-beb26ab9d0b7@suswa.mountain>
Date: Tue, 24 Jun 2025 01:55:59 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Colin Ian King <colin.i.king@...il.com>
Cc: Dave Penkler <dpenkler@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Michael Rubin <matchstick@...erthere.org>,
	linux-staging@...ts.linux.dev, kernel-janitors@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] staging: gpib: fix unset padding field copy back
 to userspace

On Tue, Jun 24, 2025 at 01:25:14AM +0300, Dan Carpenter wrote:
> On Mon, Jun 23, 2025 at 11:09:58PM +0100, Colin Ian King wrote:
> > The introduction of a padding field in the gpib_board_info_ioctl is
> > showing up as initialized data on the stack frame being copyied back
> > to userspace in function board_info_ioctl. The simplest fix is to
> > initialize the entire struct to zero to ensure all unassigned padding
> > fields are zero'd before being copied back to userspace.
> > 
> > Fixes: b8394732ff0c ("staging: gpib: Add bit and byte padding to ioctl structs")
> > Signed-off-by: Colin Ian King <colin.i.king@...il.com>
> > ---
> 
> The fix is good, but the bug has been there since the driver was
> introduced, it's only just now that the static checkers have started
> catching it.  Oddly/sadly Smatch doesn't catch this one.  I'll have to
> investigate.
> 
> Fixes: 9dde4559e939 ("staging: gpib: Add GPIB common core driver")
> 
> regards,
> dan carpenter

Fixed.

We should still print a warning about empty bits after a bitfield.
I bet fixing that will find a dozen bugs at least...

regards,
dan carpenter

--- >8 ---
[PATCH] rosenberg: warn about uninitialized bitfields

You could have a bitfield where not all the bits are set.  Warn about
that.

Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
 check_rosenberg.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/check_rosenberg.c b/check_rosenberg.c
index 22df8a3e5b64..80e15f2cf5ec 100644
--- a/check_rosenberg.c
+++ b/check_rosenberg.c
@@ -221,8 +221,12 @@ static int member_uninitialized(char *name, struct symbol *outer, struct symbol
 	struct symbol *base;
 	struct sm_state *sm;
 
+	if (!member->ident)
+		return FALSE;
 	base = get_base_type(member);
-	if (!base || base->type != SYM_BASETYPE || !member->ident)
+	if (!base)
+		return FALSE;
+	if (base->type != SYM_BASETYPE && base->type != SYM_BITFIELD)
 		return FALSE;
 
 	if (pointer)
-- 
2.47.2