netfilter: xt_IDLETIMER: reject rev0 reuse of ALARM timer labels

[ Upstream commit 329f0b9b48ee6ab59d1ab72fef55fe8c6463a6cf ]

IDLETIMER revision 0 rules reuse existing timers by label and always call
mod_timer() on timer->timer.

If the label was created first by revision 1 with XT_IDLETIMER_ALARM,
the object uses alarm timer semantics and timer->timer is never initialized.
Reusing that object from revision 0 causes mod_timer() on an uninitialized
timer_list, triggering debugobjects warnings and possible panic when
panic_on_warn=1.

Fix this by rejecting revision 0 rule insertion when an existing timer with
the same label is of ALARM type.

BUG=b/494228396
TEST=presubmit
RELEASE_NOTE=Fixed KCTF-329f0b9 in the Linux kernel.

cos-patch: security-moderate
Fixes: 68983a354a65 ("netfilter: xtables: Add snapshot of hardidletimer target")
Co-developed-by: Yifan Wu <yifanwucs@gmail.com>
Change-Id: I8cde52413bc884b0d5fb8d40bb1a2a9fa7a73986
Signed-off-by: Yifan Wu <yifanwucs@gmail.com>
Co-developed-by: Juefei Pu <tomapufckgml@gmail.com>
Signed-off-by: Juefei Pu <tomapufckgml@gmail.com>
Signed-off-by: Yuan Tan <tanyuan98@outlook.com>
Signed-off-by: Xin Liu <dstsmallbird@foxmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/139241
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Miri Amarilio <mirilio@google.com>