f0e386ee0c
Before the commit 896fbe20b4e2333fb55 ("printk: use the lockless
ringbuffer"), msg_print_text() would only write up to size-1 bytes
into the provided buffer. Some callers expect this behavior and
append a terminator to returned string. In particular:
arch/powerpc/xmon/xmon.c:dump_log_buf()
arch/um/kernel/kmsg_dump.c:kmsg_dumper_stdout()
msg_print_text() has been replaced by record_print_text(), which
currently fills the full size of the buffer. This causes a
buffer overflow for the above callers.
Change record_print_text() so that it will only use size-1 bytes
for text data. Also, for paranoia sakes, add a terminator after
the text data.
And finally, document this behavior so that it is clear that only
size-1 bytes are used and a terminator is added.
Fixes: 896fbe20b4e2333fb55 ("printk: use the lockless ringbuffer")
Cc: stable@vger.kernel.org # 5.10+
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210114170412.4819-1-john.ogness@linutronix.de
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.