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Subject[PATCH AUTOSEL 5.4 157/459] selinux: revert "stop passing MAY_NOT_BLOCK to the AVC upon follow_link"
Date
From: Stephen Smalley <sds@tycho.nsa.gov>

[ Upstream commit 1a37079c236d55fb31ebbf4b59945dab8ec8764c ]

This reverts commit e46e01eebbbc ("selinux: stop passing MAY_NOT_BLOCK
to the AVC upon follow_link"). The correct fix is to instead fall
back to ref-walk if audit is required irrespective of the specific
audit data type. This is done in the next commit.

Fixes: e46e01eebbbc ("selinux: stop passing MAY_NOT_BLOCK to the AVC upon follow_link")
Reported-by: Will Deacon <will@kernel.org>
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
security/selinux/avc.c | 24 ++++++++++++++++++++++--
security/selinux/hooks.c | 5 +++--
security/selinux/include/avc.h | 5 +++++
3 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/security/selinux/avc.c b/security/selinux/avc.c
index ecd3829996aa4..74c43ebe34bb8 100644
--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -862,8 +862,9 @@ static int avc_update_node(struct selinux_avc *avc,
* permissive mode that only appear when in enforcing mode.
*
* See the corresponding handling in slow_avc_audit(), and the
- * logic in selinux_inode_permission for the MAY_NOT_BLOCK flag,
- * which is transliterated into AVC_NONBLOCKING.
+ * logic in selinux_inode_follow_link and selinux_inode_permission
+ * for the VFS MAY_NOT_BLOCK flag, which is transliterated into
+ * AVC_NONBLOCKING for avc_has_perm_noaudit().
*/
if (flags & AVC_NONBLOCKING)
return 0;
@@ -1205,6 +1206,25 @@ int avc_has_perm(struct selinux_state *state, u32 ssid, u32 tsid, u16 tclass,
return rc;
}

+int avc_has_perm_flags(struct selinux_state *state,
+ u32 ssid, u32 tsid, u16 tclass, u32 requested,
+ struct common_audit_data *auditdata,
+ int flags)
+{
+ struct av_decision avd;
+ int rc, rc2;
+
+ rc = avc_has_perm_noaudit(state, ssid, tsid, tclass, requested,
+ (flags & MAY_NOT_BLOCK) ? AVC_NONBLOCKING : 0,
+ &avd);
+
+ rc2 = avc_audit(state, ssid, tsid, tclass, requested, &avd, rc,
+ auditdata, flags);
+ if (rc2)
+ return rc2;
+ return rc;
+}
+
u32 avc_policy_seqno(struct selinux_state *state)
{
return state->avc->avc_cache.latest_notif;
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 9625b99e677fd..9943539457906 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3008,8 +3008,9 @@ static int selinux_inode_follow_link(struct dentry *dentry, struct inode *inode,
if (IS_ERR(isec))
return PTR_ERR(isec);

- return avc_has_perm(&selinux_state,
- sid, isec->sid, isec->sclass, FILE__READ, &ad);
+ return avc_has_perm_flags(&selinux_state,
+ sid, isec->sid, isec->sclass, FILE__READ, &ad,
+ rcu ? MAY_NOT_BLOCK : 0);
}

static noinline int audit_inode_permission(struct inode *inode,
diff --git a/security/selinux/include/avc.h b/security/selinux/include/avc.h
index 7be0e1e90e8be..74ea50977c201 100644
--- a/security/selinux/include/avc.h
+++ b/security/selinux/include/avc.h
@@ -153,6 +153,11 @@ int avc_has_perm(struct selinux_state *state,
u32 ssid, u32 tsid,
u16 tclass, u32 requested,
struct common_audit_data *auditdata);
+int avc_has_perm_flags(struct selinux_state *state,
+ u32 ssid, u32 tsid,
+ u16 tclass, u32 requested,
+ struct common_audit_data *auditdata,
+ int flags);

int avc_has_extended_perms(struct selinux_state *state,
u32 ssid, u32 tsid, u16 tclass, u32 requested,
--
2.20.1
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