4.9-stable patches

added patches:
	smack-fix-use-after-free-in-smk_write_relabel_self.patch

diff --git a/queue-4.9/series b/queue-4.9/series
index 5de4e87b566dd0cf186de3f49b4dba90b4c479ee..d059cd84d146a39b2ef94a90a00d6f76bdf56c87 100644 (file)
--- a/queue-4.9/series
+++ b/queue-4.9/series
@@ -75,3 +75,4 @@ vxlan-ensure-fdb-dump-is-performed-under-rcu.patch
 net-lan78xx-replace-bogus-endpoint-lookup.patch
 revert-vxlan-fix-tos-value-before-xmit.patch
 usb-hso-check-for-return-value-in-hso_serial_common_create.patch
+smack-fix-use-after-free-in-smk_write_relabel_self.patch

diff --git a/queue-4.9/smack-fix-use-after-free-in-smk_write_relabel_self.patch b/queue-4.9/smack-fix-use-after-free-in-smk_write_relabel_self.patch
new file mode 100644 (file)
index 0000000..ee516d6
--- /dev/null
+++ b/queue-4.9/smack-fix-use-after-free-in-smk_write_relabel_self.patch
@@ -0,0 +1,79 @@
+From beb4ee6770a89646659e6a2178538d2b13e2654e Mon Sep 17 00:00:00 2001
+From: Eric Biggers <ebiggers@google.com>
+Date: Wed, 8 Jul 2020 13:15:20 -0700
+Subject: Smack: fix use-after-free in smk_write_relabel_self()
+
+From: Eric Biggers <ebiggers@google.com>
+
+commit beb4ee6770a89646659e6a2178538d2b13e2654e upstream.
+
+smk_write_relabel_self() frees memory from the task's credentials with
+no locking, which can easily cause a use-after-free because multiple
+tasks can share the same credentials structure.
+
+Fix this by using prepare_creds() and commit_creds() to correctly modify
+the task's credentials.
+
+Reproducer for "BUG: KASAN: use-after-free in smk_write_relabel_self":
+
+       #include <fcntl.h>
+       #include <pthread.h>
+       #include <unistd.h>
+
+       static void *thrproc(void *arg)
+       {
+               int fd = open("/sys/fs/smackfs/relabel-self", O_WRONLY);
+               for (;;) write(fd, "foo", 3);
+       }
+
+       int main()
+       {
+               pthread_t t;
+               pthread_create(&t, NULL, thrproc, NULL);
+               thrproc(NULL);
+       }
+
+Reported-by: syzbot+e6416dabb497a650da40@syzkaller.appspotmail.com
+Fixes: 38416e53936e ("Smack: limited capability for changing process label")
+Cc: <stable@vger.kernel.org> # v4.4+
+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/smackfs.c |   13 +++++++++++--
+ 1 file changed, 11 insertions(+), 2 deletions(-)
+
+--- a/security/smack/smackfs.c
++++ b/security/smack/smackfs.c
+@@ -2741,7 +2741,6 @@ static int smk_open_relabel_self(struct
+ static ssize_t smk_write_relabel_self(struct file *file, const char __user *buf,
+                               size_t count, loff_t *ppos)
+ {
+-      struct task_smack *tsp = current_security();
+       char *data;
+       int rc;
+       LIST_HEAD(list_tmp);
+@@ -2766,11 +2765,21 @@ static ssize_t smk_write_relabel_self(st
+       kfree(data);
+ 
+       if (!rc || (rc == -EINVAL && list_empty(&list_tmp))) {
++              struct cred *new;
++              struct task_smack *tsp;
++
++              new = prepare_creds();
++              if (!new) {
++                      rc = -ENOMEM;
++                      goto out;
++              }
++              tsp = new->security;
+               smk_destroy_label_list(&tsp->smk_relabel);
+               list_splice(&list_tmp, &tsp->smk_relabel);
++              commit_creds(new);
+               return count;
+       }
+-
++out:
+       smk_destroy_label_list(&list_tmp);
+       return rc;
+ }