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From: Arnd Bergmann <arnd@kernel.org>
To: linux-kernel@vger.kernel.org, Martin Sebor <msebor@gcc.gnu.org>,
	Serge Hallyn <serge@hallyn.com>, James Morris <jmorris@namei.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
	x86@kernel.org, Ning Sun <ning.sun@intel.com>,
	Jani Nikula <jani.nikula@linux.intel.com>,
	Kalle Valo <kvalo@codeaurora.org>,
	Simon Kelley <simon@thekelleys.org.uk>,
	James Smart <james.smart@broadcom.com>,
	"James E.J. Bottomley" <jejb@linux.ibm.com>,
	Anders Larsen <al@alarsen.net>, Tejun Heo <tj@kernel.org>,
	Imre Deak <imre.deak@intel.com>,
	linux-arm-kernel@lists.infradead.org,
	tboot-devel@lists.sourceforge.net,
	intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	ath11k@lists.infradead.org, linux-wireless@vger.kernel.org,
	netdev@vger.kernel.org, linux-scsi@vger.kernel.org,
	cgroups@vger.kernel.org, linux-security-module@vger.kernel.org,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Kees Cook <keescook@chromium.org>,
	Miklos Szeredi <mszeredi@redhat.com>,
	Tycho Andersen <tycho@tycho.pizza>
Subject: [PATCH 03/11] security: commoncap: fix -Wstringop-overread warning
Date: Mon, 22 Mar 2021 17:02:41 +0100
Message-ID: <20210322160253.4032422-4-arnd@kernel.org> (raw)
In-Reply-To: <20210322160253.4032422-1-arnd@kernel.org>

From: Arnd Bergmann <arnd@arndb.de>

gcc-11 introdces a harmless warning for cap_inode_getsecurity:

security/commoncap.c: In function ‘cap_inode_getsecurity’:
security/commoncap.c:440:33: error: ‘memcpy’ reading 16 bytes from a region of size 0 [-Werror=stringop-overread]
  440 |                                 memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
      |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The problem here is that tmpbuf is initialized to NULL, so gcc assumes
it is not accessible unless it gets set by vfs_getxattr_alloc().  This is
a legitimate warning as far as I can tell, but the code is correct since
it correctly handles the error when that function fails.

Add a separate NULL check to tell gcc about it as well.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 security/commoncap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/commoncap.c b/security/commoncap.c
index 28f4d25480df..9a36ed6dd737 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -400,7 +400,7 @@ int cap_inode_getsecurity(struct user_namespace *mnt_userns,
 				      &tmpbuf, size, GFP_NOFS);
 	dput(dentry);
 
-	if (ret < 0)
+	if (ret < 0 || !tmpbuf)
 		return ret;
 
 	fs_ns = inode->i_sb->s_user_ns;
-- 
2.29.2


  parent reply index

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-22 16:02 [PATCH 00/11] treewide: address gcc-11 -Wstringop-overread warnings Arnd Bergmann
2021-03-22 16:02 ` [PATCH 01/11] x86: compressed: avoid gcc-11 -Wstringop-overread warning Arnd Bergmann
2021-03-22 16:02 ` [PATCH 02/11] x86: tboot: avoid Wstringop-overread-warning Arnd Bergmann
2021-03-22 20:29   ` Ingo Molnar
2021-03-22 21:39     ` Arnd Bergmann
2021-03-22 22:07     ` Martin Sebor
2021-03-22 22:49       ` Arnd Bergmann
2021-03-22 23:13       ` Ingo Molnar
2021-03-24  9:11       ` David Laight
2021-03-24 10:39         ` David Laight
2021-03-22 16:02 ` Arnd Bergmann [this message]
2021-03-22 16:31   ` [PATCH 03/11] security: commoncap: fix -Wstringop-overread warning Christian Brauner
2021-03-24 20:50   ` James Morris
2021-03-22 16:02 ` [PATCH 04/11] ath11: Wstringop-overread warning Arnd Bergmann
2021-03-22 16:02 ` [PATCH 05/11] qnx: avoid -Wstringop-overread warning Arnd Bergmann
2021-03-22 16:02 ` [PATCH 06/11] cgroup: fix -Wzero-length-bounds warnings Arnd Bergmann
2021-03-30  8:41   ` Michal Koutný
2021-03-30  9:00     ` Arnd Bergmann
2021-03-30 14:44       ` Michal Koutný
2021-03-22 16:02 ` [PATCH 07/11] ARM: sharpsl_param: work around -Wstringop-overread warning Arnd Bergmann
2021-03-22 16:02 ` [PATCH 08/11] atmel: avoid gcc -Wstringop-overflow warning Arnd Bergmann
2021-03-22 16:02 ` [PATCH 09/11] scsi: lpfc: fix gcc -Wstringop-overread warning Arnd Bergmann
2021-03-22 16:02 ` [PATCH 10/11] drm/i915: avoid stringop-overread warning on pri_latency Arnd Bergmann
2021-03-24 15:30   ` Jani Nikula
2021-03-24 17:22     ` Ville Syrjälä
2021-03-22 16:02 ` [PATCH 11/11] [RFC] drm/i915/dp: fix array overflow warning Arnd Bergmann
2021-03-25  8:05   ` Jani Nikula
2021-03-25  9:53     ` Arnd Bergmann
2021-03-25 14:49       ` Martin Sebor
2021-03-30 10:56   ` Hans de Goede
2021-04-06  4:53 ` [PATCH 00/11] treewide: address gcc-11 -Wstringop-overread warnings Martin K. Petersen

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