On 2024/5/20 19:14, Baokun Li wrote:
On 2024/5/20 17:24, Jingbo Xu wrote:
On 5/20/24 5:07 PM, Baokun Li wrote:
On 2024/5/20 16:43, Jingbo Xu wrote:
On 5/15/24 4:45 PM, libaokun@xxxxxxxxxxxxxxx wrote:
From: Baokun Li <libaokun1@xxxxxxxxxx>
SNIP
To avoid this, allocate a new anonymous fd only if no anonymous fd has
been allocated (ondemand_id == 0) or if the previously allocated
anonymous
fd has been closed (ondemand_id == -1). Moreover, returns an error if
ondemand_id is valid, letting the daemon know that the current userland
restore logic is abnormal and needs to be checked.
Fixes: c8383054506c ("cachefiles: notify the user daemon when looking
up cookie")
Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
The LOCs of this fix is quite under control. But still it seems that
the worst consequence is that the (potential) malicious daemon gets
hung. No more effect to the system or other processes. Or does a
non-malicious daemon have any chance having the same issue?
If we enable hung_task_panic, it may cause panic to crash the server.
Then this issue has nothing to do with this patch? As long as a
malicious daemon doesn't close the anonymous fd after umounting, then I
guess a following attempt of mounting cookie with the same name will
also wait and hung there?
Yes, a daemon that only reads requests but doesn't process them will
cause hung，but the daemon will obey the basic constraints when we
test it.
If we'd really like to enhanace this ("hung_task_panic"), I think
you'd better to switch wait_for_completion() to
wait_for_completion_killable() at least IMHO anyway.
Thanks,
Gao Xiang
