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f0d0277796
When __netpoll_setup() is called directly, instead of through
netpoll_setup(), the np->skb_pool list head isn't initialized.
If skb_pool_flush() is later called, then we hit a NULL pointer
in skb_queue_purge_reason(). This can be seen with this repro,
when CONFIG_NETCONSOLE is enabled as a module:
ip tuntap add mode tap tap0
ip link add name br0 type bridge
ip link set dev tap0 master br0
modprobe netconsole netconsole=4444@10.0.0.1/br0,9353@10.0.0.2/
rmmod netconsole
The backtrace is:
BUG: kernel NULL pointer dereference, address: 0000000000000008
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
... ... ...
Call Trace:
<TASK>
__netpoll_free+0xa5/0xf0
br_netpoll_cleanup+0x43/0x50 [bridge]
do_netpoll_cleanup+0x43/0xc0
netconsole_netdev_event+0x1e3/0x300 [netconsole]
unregister_netdevice_notifier+0xd9/0x150
cleanup_module+0x45/0x920 [netconsole]
__se_sys_delete_module+0x205/0x290
do_syscall_64+0x70/0x150
entry_SYSCALL_64_after_hwframe+0x76/0x7e
Move the skb_pool list setup and initial skb fill into __netpoll_setup().
Fixes: 221a9c1df7 ("net: netpoll: Individualize the skb pool")
Signed-off-by: John Sperbeck <jsperbeck@google.com>
Reviewed-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20250114011354.2096812-1-jsperbeck@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.