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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+0eefc1e06a77d327a056@syzkaller.appspotmail.com,
        Eric Biggers <ebiggers@google.com>,
        Casey Schaufler <casey@schaufler-ca.com>
Subject: [PATCH 4.4 35/36] smack: use GFP_NOFS while holding inode_smack::smk_lock
Date:   Sun,  6 Oct 2019 19:19:17 +0200
Message-Id: <20191006171100.911332251@linuxfoundation.org>
In-Reply-To: <20191006171038.266461022@linuxfoundation.org>
References: <20191006171038.266461022@linuxfoundation.org>
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From: Eric Biggers <ebiggers@google.com>

commit e5bfad3d7acc5702f32aafeb388362994f4d7bd0 upstream.

inode_smack::smk_lock is taken during smack_d_instantiate(), which is
called during a filesystem transaction when creating a file on ext4.
Therefore to avoid a deadlock, all code that takes this lock must use
GFP_NOFS, to prevent memory reclaim from waiting for the filesystem
transaction to complete.

Reported-by: syzbot+0eefc1e06a77d327a056@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 security/smack/smack_access.c |    4 ++--
 security/smack/smack_lsm.c    |    2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

--- a/security/smack/smack_access.c
+++ b/security/smack/smack_access.c
@@ -474,7 +474,7 @@ char *smk_parse_smack(const char *string
 	if (i == 0 || i >= SMK_LONGLABEL)
 		return ERR_PTR(-EINVAL);
 
-	smack = kzalloc(i + 1, GFP_KERNEL);
+	smack = kzalloc(i + 1, GFP_NOFS);
 	if (smack == NULL)
 		return ERR_PTR(-ENOMEM);
 
@@ -545,7 +545,7 @@ struct smack_known *smk_import_entry(con
 	if (skp != NULL)
 		goto freeout;
 
-	skp = kzalloc(sizeof(*skp), GFP_KERNEL);
+	skp = kzalloc(sizeof(*skp), GFP_NOFS);
 	if (skp == NULL) {
 		skp = ERR_PTR(-ENOMEM);
 		goto freeout;
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -268,7 +268,7 @@ static struct smack_known *smk_fetch(con
 	if (ip->i_op->getxattr == NULL)
 		return ERR_PTR(-EOPNOTSUPP);
 
-	buffer = kzalloc(SMK_LONGLABEL, GFP_KERNEL);
+	buffer = kzalloc(SMK_LONGLABEL, GFP_NOFS);
 	if (buffer == NULL)
 		return ERR_PTR(-ENOMEM);