Re: [PATCH] KEYS: Do not cache key in task struct if key is requested from kernel thread

[Jarkko Sakkinen <jarkko@kernel.org>]

On Mon, Mar 13, 2023 at 10:48:29AM +0530, Bharath SM wrote:
> Linux kernel cifs module uses dns_resolver for dns resolution and
> dns_resolver will use kernel keys infrastructure for key management.
> Cifs module calls dns_query during reconnect for dns resolution, we noticed
> an issue with dns resolution requests during reconnect operations from cifs.
> Where the dns_query was failing by returning EKEYEXPIRED to cifs. And
> this issue was
> happening only when CONFIG_KEYS_REQUEST_CACHE was enabled.
> Further debugging the keys subsystem and discussing with david howells revealed
> this issue in keys subsystem.
> 
> To reproduce the issue mount a few SMB shares on device with
> nosharesock mount option and try disconnecting connections a few times
> using "ss -K src dport 445".
> 
> Logs from dns_resolver:
> Notice that 2nd time, we can see dns_query returning -127(EKEYEXPIRED)
> 
> Disconnected first time and got right response for dns_query:
> 
> [Mon Mar 13 05:05:23 2023] [cifsd ] ==>
> dns_query((null),storagesouthcus1.file.core.windows.net,38,(null))
> [Mon Mar 13 05:05:23 2023] [cifsd ] call
> request_key(,storagesouthcus1.file.core.windows.net,)
> [Mon Mar 13 05:05:23 2023] [cifsd ] ==>
> dns_query((null),storagesouthcus1.file.core.windows.net,38,(null))
> [Mon Mar 13 05:05:23 2023] [cifsd ] call
> request_key(,storagesouthcus1.file.core.windows.net,)
> [Mon Mar 13 05:05:23 2023] [cifsd ] ==>
> dns_resolver_cmp(storagesouthcus1.file.core.windows.net,storagesouthcus1.file.core.windows.net)
> [Mon Mar 13 05:05:23 2023] [cifsd ] <== dns_resolver_cmp() = 1
> [Mon Mar 13 05:05:23 2023] [key.dn] ==> dns_resolver_preparse('
> 20.150.20.136',14)
> [Mon Mar 13 05:05:23 2023] [key.dn] no options
> [Mon Mar 13 05:05:23 2023] [key.dn] store result
> [Mon Mar 13 05:05:23 2023] [key.dn] <== dns_resolver_preparse() = 0
> [Mon Mar 13 05:05:23 2023] [cifsd ] <== dns_query() = 13
> [Mon Mar 13 05:05:23 2023] [cifsd ] <== dns_query() = 13
> 
> Disconnected second time, but this time we can see one of the
> dns_query request is failing with -127
> 
> [Mon Mar 13 05:05:30 2023] [cifsd ] ==>
> dns_query((null),storagesouthcus1.file.core.windows.net,38,(null))
> [Mon Mar 13 05:05:30 2023] [cifsd ] call
> request_key(,storagesouthcus1.file.core.windows.net,)
> [Mon Mar 13 05:05:30 2023] [cifsd ] ==>
> dns_query((null),storagesouthcus1.file.core.windows.net,38,(null))
> [Mon Mar 13 05:05:30 2023] [cifsd ] call
> request_key(,storagesouthcus1.file.core.windows.net,)
> [Mon Mar 13 05:05:30 2023] [cifsd ] ==>
> dns_resolver_cmp(storagesouthcus1.file.core.windows.net,storagesouthcus1.file.core.windows.net)
> [Mon Mar 13 05:05:30 2023] [cifsd ] <== dns_resolver_cmp() = 1
> [Mon Mar 13 05:05:30 2023] [cifsd ] <== dns_query() = -127
> [Mon Mar 13 05:05:30 2023] [key.dn] ==> dns_resolver_preparse('
> 20.150.20.136',14)
> [Mon Mar 13 05:05:30 2023] [key.dn] no options
> [Mon Mar 13 05:05:30 2023] [key.dn] store result
> [Mon Mar 13 05:05:30 2023] [key.dn] <== dns_resolver_preparse() = 0
> [Mon Mar 13 05:05:30 2023] [cifsd ] <== dns_query() = 13

Please summarize this to the commit message it is useful stuff. With
this report included the patch could should also have a fixes tag.

BR, Jarkko