linux-stable.git/drivers/net/netconsole.c, branch linux-6.10.y

net: netconsole: Disable target before netpoll cleanup

2024-08-03T07:00:30+00:00

commit 97d9fba9a812cada5484667a46e14a4c976ca330 upstream.

Currently, netconsole cleans up the netpoll structure before disabling
the target. This approach can lead to race conditions, as message
senders (write_ext_msg() and write_msg()) check if the target is
enabled before using netpoll. The sender can validate that the target is
enabled, but, the netpoll might be de-allocated already, causing
undesired behaviours.

This patch reverses the order of operations:
1. Disable the target
2. Clean up the netpoll structure

This change eliminates the potential race condition, ensuring that
no messages are sent through a partially cleaned-up netpoll structure.

Fixes: 2382b15bcc39 ("netconsole: take care of NETDEV_UNREGISTER event")
Cc: stable@vger.kernel.org
Signed-off-by: Breno Leitao 
Reviewed-by: Eric Dumazet 
Link: https://patch.msgid.link/20240712143415.1141039-1-leitao@debian.org
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

net: netconsole: Add continuation line prefix to userdata messages

2024-03-11T21:07:57+00:00

Add a space (' ') prefix to every userdata line to match docs for
dev-kmsg. To account for this extra character in each userdata entry,
reduce userdata entry names (directory name) from 54 characters to 53.

According to the dev-kmsg docs, a space is used for subsequent lines to
mark them as continuation lines.

> A line starting with ' ', is a continuation line, adding
> key/value pairs to the log message, which provide the machine
> readable context of the message, for reliable processing in
> userspace.

Testing for this patch::

 cd /sys/kernel/config/netconsole && mkdir cmdline0
 cd cmdline0
 mkdir userdata/test && echo "hello" > userdata/test/value
 mkdir userdata/test2 && echo "hello2" > userdata/test2/value
 echo "message" > /dev/kmsg

Outputs::

 6.8.0-rc5-virtme,12,493,231373579,-;message
  test=hello
  test2=hello2

And I confirmed all testing works as expected from the original patchset

Fixes: df03f830d099 ("net: netconsole: cache userdata formatted string in netconsole_target")
Signed-off-by: Matthew Wood 
Reviewed-by: Breno Leitao 
Link: https://lore.kernel.org/r/20240308002525.248672-1-thepacketgeek@gmail.com
Signed-off-by: Jakub Kicinski

net: netconsole: append userdata to fragmented netconsole messages

2024-02-09T10:23:46+00:00

Regardless of whether the original message body or formatted userdata
exceeds the MAX_PRINT_CHUNK, append userdata to the netconsole message
starting with the first chunk that has available space after writing the
body.

Co-developed-by: Breno Leitao 
Signed-off-by: Breno Leitao 
Signed-off-by: Matthew Wood 
Signed-off-by: David S. Miller

net: netconsole: append userdata to netconsole messages

2024-02-09T10:23:46+00:00

Append userdata to outgoing unfragmented (<1000 bytes) netconsole messages.
When sending messages the userdata string is already formatted and stored
in netconsole_target->userdata_complete.

Always write the outgoing message to buf, so userdata can be appended in
a standard fashion. This is a change from only using buf when the
release needs to be prepended to the message.

Co-developed-by: Breno Leitao 
Signed-off-by: Breno Leitao 
Signed-off-by: Matthew Wood 
Signed-off-by: David S. Miller

net: netconsole: cache userdata formatted string in netconsole_target

2024-02-09T10:23:45+00:00

Store a formatted string for userdata that will be appended to netconsole
messages. The string has a capacity of 4KB, as calculated by the userdatum
entry length of 256 bytes and a max of 16 userdata entries.

Update the stored netconsole_target->userdata_complete string with the new
formatted userdata values when a userdatum is created, edited, or
removed. Each userdata entry contains a trailing newline, which will be
formatted as such in netconsole messages::

    6.7.0-rc8-virtme,12,500,1646292204,-;test
    release=foo
    something=bar
    6.7.0-rc8-virtme,12,500,1646292204,-;another test
    release=foo
    something=bar

Enforcement of MAX_USERDATA_ITEMS is done in userdatum_make_item;
update_userdata will not check for this case but will skip any userdata
children over the limit of MAX_USERDATA_ITEMs.

If a userdata entry/dir is created but no value is provided, that entry
will be skipped. This is in part because update_userdata() can't be
called in userdatum_make_item() since the item will not have been added
to the userdata config_group children yet. To preserve the experience of
adding an empty userdata that doesn't show up in the netconsole
messages, purposefully skip empty userdata items even when
update_userdata() can be called.

Co-developed-by: Breno Leitao 
Signed-off-by: Breno Leitao 
Signed-off-by: Matthew Wood 
Signed-off-by: David S. Miller

net: netconsole: add a userdata config_group member to netconsole_target

2024-02-09T10:23:45+00:00

Create configfs machinery for netconsole userdata appending, which depends
on CONFIG_NETCONSOLE_DYNAMIC (for configfs interface). Add a userdata
config_group to netconsole_target for managing userdata entries as a tree
under the netconsole configfs subsystem. Directory names created under the
userdata directory become userdatum keys; the userdatum value is the
content of the value file.

Include the minimum-viable-changes for userdata configfs config_group.
init_target_config_group() ties in the complete configfs machinery to
avoid unused func/variable errors during build. Initializing the
netconsole_target->group is moved to init_target_config_group, which
will also init and add the userdata config_group.

Each userdatum entry has a limit of 256 bytes (54 for
the key/directory, 200 for the value, and 2 for '=' and '\n'
characters), which is enforced by the configfs functions for updating
the userdata config_group.

When a new netconsole_target is created, initialize the userdata
config_group and add it as a default group for netconsole_target
config_group, allowing the userdata configfs sub-tree to be presented
in the netconsole configfs tree under the userdata directory.

Co-developed-by: Breno Leitao 
Signed-off-by: Breno Leitao 
Signed-off-by: Matthew Wood 
Signed-off-by: David S. Miller

net: netconsole: move newline trimming to function

2024-02-09T10:23:45+00:00

Move newline trimming logic from `dev_name_store()` to a new function
(trim_newline()) for shared use in netconsole.c

Signed-off-by: Matthew Wood 
Signed-off-by: David S. Miller

net: netconsole: move netconsole_target config_item to config_group

2024-02-09T10:23:45+00:00

In order to support a nested userdata config_group in later patches,
use a config_group for netconsole_target instead of a
config_item. It's a no-op functionality-wise, since
config_group maintains all features of a config_item via the cg_item
member.

Signed-off-by: Matthew Wood 
Reviewed-by: Breno Leitao 
Signed-off-by: David S. Miller

net: netconsole: cleanup formatting lints

2024-02-09T10:23:45+00:00

Address checkpatch lint suggestions in preparation for later changes

Signed-off-by: Matthew Wood 
Reviewed-by: Breno Leitao 
Signed-off-by: David S. Miller

netconsole: Attach cmdline target to dynamic target

2023-10-14T00:26:38+00:00

Enable the attachment of a dynamic target to the target created during
boot time. The boot-time targets are named as "cmdline\d", where "\d" is
a number starting at 0.

If the user creates a dynamic target named "cmdline0", it will attach to
the first target created at boot time (as defined in the
`netconsole=...` command line argument). `cmdline1` will attach to the
second target and so forth.

If there is no netconsole target created at boot time, then, the target
name could be reused.

Relevant design discussion:
https://lore.kernel.org/all/ZRWRal5bW93px4km@gmail.com/

Suggested-by: Joel Becker 
Signed-off-by: Breno Leitao 
Link: https://lore.kernel.org/r/20231012111401.333798-4-leitao@debian.org
Signed-off-by: Jakub Kicinski