linux-toradex.git/drivers/net/netconsole.c, branch v6.18

netconsole: Acquire su_mutex before navigating configs hierarchy

2025-11-01T00:45:06+00:00

There is a race between operations that iterate over the userdata
cg_children list and concurrent add/remove of userdata items through
configfs. The update_userdata() function iterates over the
nt->userdata_group.cg_children list, and count_extradata_entries() also
iterates over this same list to count nodes.

Quoting from Documentation/filesystems/configfs.rst:
> A subsystem can navigate the cg_children list and the ci_parent pointer
> to see the tree created by the subsystem.  This can race with configfs'
> management of the hierarchy, so configfs uses the subsystem mutex to
> protect modifications.  Whenever a subsystem wants to navigate the
> hierarchy, it must do so under the protection of the subsystem
> mutex.

Without proper locking, if a userdata item is added or removed
concurrently while these functions are iterating, the list can be
accessed in an inconsistent state. For example, the list_for_each() loop
can reach a node that is being removed from the list by list_del_init()
which sets the nodes' .next pointer to point to itself, so the loop will
never end (or reach the WARN_ON_ONCE in update_userdata() ).

Fix this by holding the configfs subsystem mutex (su_mutex) during all
operations that iterate over cg_children.
This includes:
- userdatum_value_store() which calls update_userdata() to iterate over
  cg_children
- All sysdata_*_enabled_store() functions which call
  count_extradata_entries() to iterate over cg_children

The su_mutex must be acquired before dynamic_netconsole_mutex to avoid
potential lock ordering issues, as configfs operations may already hold
su_mutex when calling into our code.

Fixes: df03f830d099 ("net: netconsole: cache userdata formatted string in netconsole_target")
Signed-off-by: Gustavo Luiz Duarte 
Link: https://patch.msgid.link/20251029-netconsole-fix-warn-v1-1-0d0dd4622f48@gmail.com
Signed-off-by: Jakub Kicinski

netconsole: Fix race condition in between reader and writer of userdata

2025-10-30T00:41:00+00:00

The update_userdata() function constructs the complete userdata string
in nt->extradata_complete and updates nt->userdata_length. This data
is then read by write_msg() and write_ext_msg() when sending netconsole
messages. However, update_userdata() was not holding target_list_lock
during this process, allowing concurrent message transmission to read
partially updated userdata.

This race condition could result in netconsole messages containing
incomplete or inconsistent userdata - for example, reading the old
userdata_length with new extradata_complete content, or vice versa,
leading to truncated or corrupted output.

Fix this by acquiring target_list_lock with spin_lock_irqsave() before
updating extradata_complete and userdata_length, and releasing it after
both fields are fully updated. This ensures that readers see a
consistent view of the userdata, preventing corruption during concurrent
access.

The fix aligns with the existing locking pattern used throughout the
netconsole code, where target_list_lock protects access to target
fields including buf[] and msgcounter that are accessed during message
transmission.

Also get rid of the unnecessary variable complete_idx, which makes it
easier to bail out of update_userdata().

Fixes: df03f830d099 ("net: netconsole: cache userdata formatted string in netconsole_target")
Signed-off-by: Gustavo Luiz Duarte 
Link: https://patch.msgid.link/20251028-netconsole-fix-race-v4-1-63560b0ae1a0@meta.com
Signed-off-by: Jakub Kicinski

netconsole: use netpoll_parse_ip_addr in local_ip_store

2025-08-13T00:32:42+00:00

Replace manual IP address parsing with a call to netpoll_parse_ip_addr
in remote_ip_store(), simplifying the code and reducing the chance of
errors.

The error message got removed, since it is not a good practice to
pr_err() if used pass a wrong value in configfs.

Signed-off-by: Breno Leitao 
Reviewed-by: Simon Horman 
Signed-off-by: Jakub Kicinski

netconsole: use netpoll_parse_ip_addr in local_ip_store

2025-08-13T00:32:42+00:00

Replace manual IP address parsing with a call to netpoll_parse_ip_addr
in local_ip_store(), simplifying the code and reducing the chance of
errors.

Also, remove the pr_err() if the user enters an invalid value in
configfs entries. pr_err() is not the best way to alert user that the
configuration is invalid.

Signed-off-by: Breno Leitao 
Reviewed-by: Simon Horman 
Signed-off-by: Jakub Kicinski

netconsole: add support for strings with new line in netpoll_parse_ip_addr

2025-08-13T00:32:42+00:00

The current IP address parsing logic fails when the input string
contains a trailing newline character. This can occur when IP
addresses are provided through configfs, which contains newlines in
a const buffer.

Teach netpoll_parse_ip_addr() how to ignore newlines at the end of the
IPs. Also, simplify the code by:

 * No need to check for separators. Try to parse ipv4, if it fails try
   ipv6 similarly to ceph_pton()
 * If ipv6 is not supported, don't call in6_pton() at all.

Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20250811-netconsole_ref-v4-2-9c510d8713a2@debian.org
Signed-off-by: Jakub Kicinski

netconsole: move netpoll_parse_ip_addr() earlier for reuse

2025-08-13T00:32:42+00:00

Move netpoll_parse_ip_addr() earlier in the file to be reused in
other functions, such as local_ip_store(). This avoids duplicate
address parsing logic and centralizes validation for both IPv4
and IPv6 string input.

No functional changes intended.

Signed-off-by: Breno Leitao 
Reviewed-by: Simon Horman 
Link: https://patch.msgid.link/20250811-netconsole_ref-v4-1-9c510d8713a2@debian.org
Signed-off-by: Jakub Kicinski

netconsole: append msgid to sysdata

2025-06-18T09:46:10+00:00

Add msgcounter to the netconsole_target struct to generate message IDs.
If the msgid_enabled attribute is true, increment msgcounter and append
msgid= to sysdata buffer before sending the message.

Signed-off-by: Gustavo Luiz Duarte 
Reviewed-by: Breno Leitao 
Signed-off-by: David S. Miller

netconsole: implement configfs for msgid_enabled

2025-06-18T09:46:10+00:00

Implement the _show and _store functions for the msgid_enabled configfs
attribute under userdata.
Set the sysdata_fields bit accordingly.

Reviewed-by: Breno Leitao 
Signed-off-by: Gustavo Luiz Duarte 
Signed-off-by: David S. Miller

netconsole: introduce 'msgid' as a new sysdata field

2025-06-18T09:46:10+00:00

This adds a new sysdata field to enable assigning a per-target unique id
to each message sent to that target. This id can later be appended as
part of sysdata, allowing targets to detect dropped netconsole messages.
Update count_extradata_entries() to take the new field into account.

Reviewed-by: Breno Leitao 
Signed-off-by: Gustavo Luiz Duarte 
Signed-off-by: David S. Miller

netconsole: improve code style in parser function

2025-06-16T22:18:34+00:00

Split assignment from conditional checks and use preferred null pointer
check style (!delim instead of == NULL) in netconsole_parser_cmdline().
This improves code readability and follows kernel coding style
conventions.

Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20250613-rework-v3-6-0752bf2e6912@debian.org
Signed-off-by: Jakub Kicinski