smack: use GFP_NOFS while holding inode_smack::smk_lock

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
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
[bwh: Backported to 3.16:
 - Drop change to smk_netlbl_mls(), where GFP_ATOMIC is used
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c
index c062e9467b62f91cb2b975f271de60755d66248c..f5ef20e8fddf2489b28fd0858ba2e3e6ae94e5a2 100644 (file)
--- a/security/smack/smack_access.c
+++ b/security/smack/smack_access.c
@@ -430,7 +430,7 @@ char *smk_parse_smack(const char *string, int len)
        if (i == 0 || i >= SMK_LONGLABEL)
                return NULL;
 
-       smack = kzalloc(i + 1, GFP_KERNEL);
+       smack = kzalloc(i + 1, GFP_NOFS);
        if (smack != NULL) {
                strncpy(smack, string, i + 1);
                smack[i] = '\0';
@@ -502,7 +502,7 @@ struct smack_known *smk_import_entry(const char *string, int len)
        if (skp != NULL)
                goto freeout;
 
-       skp = kzalloc(sizeof(*skp), GFP_KERNEL);
+       skp = kzalloc(sizeof(*skp), GFP_NOFS);
        if (skp == NULL)
                goto freeout;
 

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 6392a6d933acc2947256d3367f5aad2bf406e5fd..b4043b7c144a73c12cc79936d12ec040b9f8b4b3 100644 (file)
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -70,7 +70,7 @@ static struct smack_known *smk_fetch(const char *name, struct inode *ip,
        if (ip->i_op->getxattr == NULL)
                return NULL;
 
-       buffer = kzalloc(SMK_LONGLABEL, GFP_KERNEL);
+       buffer = kzalloc(SMK_LONGLABEL, GFP_NOFS);
        if (buffer == NULL)
                return NULL;