selinux: do not check open perm on ftruncate call
Use the ATTR_FILE attribute to distinguish between truncate()
and ftruncate() system calls. The two other cases where
do_truncate is called with a filp (and therefore ATTR_FILE is set)
are for coredump files and for open(O_TRUNC). In both of those cases
the open permission has already been checked during file open and
therefore does not need to be repeated.
Commit 95dbf739313f ("SELinux: check OPEN on truncate calls")
fixed a major issue where domains were allowed to truncate files
without the open permission. However, it introduced a new bug where
a domain with the write permission can no longer ftruncate files
without the open permission, even when they receive an already open
file.
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <pmoore@redhat.com>
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index e4369d8..7cd71ce 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2946,7 +2946,8 @@
ATTR_ATIME_SET | ATTR_MTIME_SET | ATTR_TIMES_SET))
return dentry_has_perm(cred, dentry, FILE__SETATTR);
- if (selinux_policycap_openperm && (ia_valid & ATTR_SIZE))
+ if (selinux_policycap_openperm && (ia_valid & ATTR_SIZE)
+ && !(ia_valid & ATTR_FILE))
av |= FILE__OPEN;
return dentry_has_perm(cred, dentry, av);