On 08/03/2010 07:11 PM, Sukadev Bhattiprolu wrote:
Restore the file-owner information for each 'struct file'. This is
essentially is like a new fcntl(F_SETOWN) and fcntl(F_SETSIG) calls,
except that the pid, uid, euid and signum values are read from the
checkpoint image.
Changelog[v3]:
- [Oren Laadan]: Ensure find_vpid() found a valid pid before
making it the file owner.
Changelog[v2]:
- [Matt Helsley, Serge Hallyn]: Don't trust uids in checkpoint image.
(added CAP_KILL check)
- Check that signal number read from the checkpoint image is valid.
(not sure it is required, since its an incomplete check for tampering)
Signed-off-by: Sukadev Bhattiprolu<sukadev@xxxxxxxxxxxxxxxxxx>
I may have missed a previous discussion on this - but: do you
plan to relate the uid/euid to the userns ?
[...]
diff --git a/fs/checkpoint.c b/fs/checkpoint.c
index ce1b4af..b5486c1 100644
--- a/fs/checkpoint.c
+++ b/fs/checkpoint.c
@@ -618,6 +618,68 @@ static int attach_file(struct file *file)
return fd;
}
+static int restore_file_owner(struct ckpt_ctx *ctx, struct ckpt_hdr_file *h,
+ struct file *file)
+{
+ int ret;
+ struct pid *pid;
+ uid_t uid, euid;
+
+ uid = h->f_owner_uid;
+ euid = h->f_owner_euid;
+
+ ckpt_debug("restore_file_owner(): uid %u, euid %u, pid %d, type %d\n",
+ uid, euid, h->f_owner_pid, h->f_owner_pid_type);
+ /*
+ * We can't trust the uids in the checkpoint image and normally need
+ * CAP_KILL. But if the uids match our ids, should be fine since we
+ * have access to the file.
+ *
+ * TODO: Move this check to __f_setown() ?
+ */
+ ret = -EACCES;
+ if (!capable(CAP_KILL)&&
+ (uid != current_uid() || euid != current_euid())) {
+ ckpt_err(ctx, ret, "image uids [%d, %d] don't match current "
+ "process uids [%d, %d] and no CAP_KILL\n",
+ uid, euid, current_uid(), current_euid());
+ return ret;
+ }
+
+ ret = -EINVAL;
+ if (!valid_signal(h->f_owner_signum)) {
+ ckpt_err(ctx, ret, "Invalid signum %d\n", h->f_owner_signum);
+ return ret;
+ }
+ file->f_owner.signum = h->f_owner_signum;
+
+ rcu_read_lock();
+
+ /*
+ * If file had a non-NULL owner and we can't find the owner after
+ * restart, return error.
+ */
+ pid = find_vpid(h->f_owner_pid);
+ if (h->f_owner_pid&& !pid)
+ ret = -ESRCH;
+ else {
+ /*
+ * TODO: Do we need 'force' to be 1 here or can it be 0 ?
+ * 'force' is used to modify the owner, if one is
+ * already set. Can it be set when we restart an
+ * application ?
+ */
+ ret = __f_setown(file, pid, h->f_owner_pid_type, uid, euid, 1);
__f_setown() does not check its pid_type argument - you need
to sanitize here, no ?
(and not that I expect the PIDTYPE_... will ever change, but -
possibly encode the PIDTYPE_... types into CKPT_PIDTYPE_... )
[...]
Oren.
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