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Subject[PATCH 5.5 107/120] selinux: revert "stop passing MAY_NOT_BLOCK to the AVC upon follow_link"
Date
From: Stephen Smalley <sds@tycho.nsa.gov>

commit 1a37079c236d55fb31ebbf4b59945dab8ec8764c upstream.

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
security/selinux/avc.c | 24 ++++++++++++++++++++++--
security/selinux/hooks.c | 5 +++--
security/selinux/include/avc.h | 5 +++++
3 files changed, 30 insertions(+), 4 deletions(-)

--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -862,8 +862,9 @@ static int avc_update_node(struct selinu
* 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;
@@ -1203,6 +1204,25 @@ int avc_has_perm(struct selinux_state *s
if (rc2)
return rc2;
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)
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3004,8 +3004,9 @@ static int selinux_inode_follow_link(str
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,
--- a/security/selinux/include/avc.h
+++ b/security/selinux/include/avc.h
@@ -153,6 +153,11 @@ int avc_has_perm(struct selinux_state *s
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,

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