diff options
| author | NeilBrown <neilb@suse.de> | 2015-03-23 13:37:39 +1100 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2015-05-11 08:13:11 -0400 |
| commit | bda0be7ad994812960e9f8f2d2757f72cb4a96cb (patch) | |
| tree | f769e7c4511b64432438f82a8426248e75a8ad7b /security | |
| parent | 7b20ea2579238f5e0da4bc93276c1b63c960c9ef (diff) | |
security: make inode_follow_link RCU-walk aware
inode_follow_link now takes an inode and rcu flag as well as the
dentry.
inode is used in preference to d_backing_inode(dentry), particularly
in RCU-walk mode.
selinux_inode_follow_link() gets dentry_has_perm() and
inode_has_perm() open-coded into it so that it can call
avc_has_perm_flags() in way that is safe if LOOKUP_RCU is set.
Calling avc_has_perm_flags() with rcu_read_lock() held means
that when avc_has_perm_noaudit calls avc_compute_av(), the attempt
to rcu_read_unlock() before calling security_compute_av() will not
actually drop the RCU read-lock.
However as security_compute_av() is completely in a read_lock()ed
region, it should be safe with the RCU read-lock held.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'security')
| -rw-r--r-- | security/capability.c | 3 | ||||
| -rw-r--r-- | security/security.c | 7 | ||||
| -rw-r--r-- | security/selinux/hooks.c | 16 |
3 files changed, 20 insertions, 6 deletions
diff --git a/security/capability.c b/security/capability.c index fae99db180ca..7d3f38fe02ba 100644 --- a/security/capability.c +++ b/security/capability.c @@ -209,7 +209,8 @@ static int cap_inode_readlink(struct dentry *dentry) return 0; } -static int cap_inode_follow_link(struct dentry *dentry) +static int cap_inode_follow_link(struct dentry *dentry, struct inode *inode, + bool rcu) { return 0; } diff --git a/security/security.c b/security/security.c index d7c30b03e144..04c8feca081a 100644 --- a/security/security.c +++ b/security/security.c @@ -581,11 +581,12 @@ int security_inode_readlink(struct dentry *dentry) return security_ops->inode_readlink(dentry); } -int security_inode_follow_link(struct dentry *dentry) +int security_inode_follow_link(struct dentry *dentry, struct inode *inode, + bool rcu) { - if (unlikely(IS_PRIVATE(d_backing_inode(dentry)))) + if (unlikely(IS_PRIVATE(inode))) return 0; - return security_ops->inode_follow_link(dentry); + return security_ops->inode_follow_link(dentry, inode, rcu); } int security_inode_permission(struct inode *inode, int mask) diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index d56a82967d5e..ffa5a642629a 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -2861,11 +2861,23 @@ static int selinux_inode_readlink(struct dentry *dentry) return dentry_has_perm(cred, dentry, FILE__READ); } -static int selinux_inode_follow_link(struct dentry *dentry) +static int selinux_inode_follow_link(struct dentry *dentry, struct inode *inode, + bool rcu) { const struct cred *cred = current_cred(); + struct common_audit_data ad; + struct inode_security_struct *isec; + u32 sid; - return dentry_has_perm(cred, dentry, FILE__READ); + validate_creds(cred); + + ad.type = LSM_AUDIT_DATA_DENTRY; + ad.u.dentry = dentry; + sid = cred_sid(cred); + isec = inode->i_security; + + return avc_has_perm_flags(sid, isec->sid, isec->sclass, FILE__READ, &ad, + rcu ? MAY_NOT_BLOCK : 0); } static noinline int audit_inode_permission(struct inode *inode, |