[PATCH 5.3 159/166] smack: use GFP_NOFS while holding inode_smack::smk_lock

Greg Kroah-Hartman
2019-10-06T17:55:01Z

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 | 6 +++---
security/smack/smack_lsm.c | 2 +-
2 files changed, 4 insertions(+), 4 deletions(-)

--- a/security/smack/smack_access.c
+++ b/security/smack/smack_access.c
@@ -465,7 +465,7 @@ 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);

@@ -500,7 +500,7 @@ int smk_netlbl_mls(int level, char *cats
if ((m & *cp) == 0)
continue;
rc = netlbl_catmap_setbit(&sap->attr.mls.cat,
- cat, GFP_KERNEL);
+ cat, GFP_NOFS);
if (rc < 0) {
netlbl_catmap_free(sap->attr.mls.cat);
return rc;
@@ -536,7 +536,7 @@ 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
@@ -288,7 +288,7 @@ static struct smack_known *smk_fetch(con
if (!(ip->i_opflags & IOP_XATTR))
return ERR_PTR(-EOPNOTSUPP);

- buffer = kzalloc(SMK_LONGLABEL, GFP_KERNEL);
+ buffer = kzalloc(SMK_LONGLABEL, GFP_NOFS);
if (buffer == NULL)
return ERR_PTR(-ENOMEM);