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[ Upstream commit165e3e17fe] A null pointer reference issue can be triggered when the response of a stream reconf request arrives after the timer is triggered, such as: send Incoming SSN Reset Request ---> CPU0: reconf timer is triggered, go to the handler code before hold sk lock <--- reply with Outgoing SSN Reset Request CPU1: process Outgoing SSN Reset Request, and set asoc->strreset_chunk to NULL CPU0: continue the handler code, hold sk lock, and try to hold asoc->strreset_chunk, crash! In Ying Xu's testing, the call trace is: [ ] BUG: kernel NULL pointer dereference, address: 0000000000000010 [ ] RIP: 0010:sctp_chunk_hold+0xe/0x40 [sctp] [ ] Call Trace: [ ] <IRQ> [ ] sctp_sf_send_reconf+0x2c/0x100 [sctp] [ ] sctp_do_sm+0xa4/0x220 [sctp] [ ] sctp_generate_reconf_event+0xbd/0xe0 [sctp] [ ] call_timer_fn+0x26/0x130 This patch is to fix it by returning from the timer handler if asoc strreset_chunk is already set to NULL. Fixes:7b9438de0c("sctp: add stream reconf timer") Reported-by: Ying Xu <yinxu@redhat.com> Signed-off-by: Xin Long <lucien.xin@gmail.com> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@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 Restructured Text 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.