John Ogness 861c2e349a printk: fix buffer overflow potential for print_text() ... commit f0e386ee0c0b71ea6f7238506a4d0965a2dbef11 upstream. Before the commit 896fbe20b4 ("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arch/powerpc/xmon/xmon.c:dump_log_buf() arch/um/kernel/kmsg_dump.c:kmsg_dumper_stdout() msg_print_text() has been replaced by record_print_text(), which currently fills the full size of the buffer.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: 896fbe20b4 ("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 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2021-01-30 13:55:20 +01:00
..
braille.c	printk: Replace strncmp() with str_has_prefix()	2019-08-16 09:54:08 +02:00
braille.h	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
console_cmdline.h	printk: Fix preferred console selection with multiple matches	2020-02-18 09:34:42 +01:00
internal.h	printk: move dictionary keys to dev_printk_info	2020-09-22 11:27:48 +02:00
Makefile	printk: add lockless ringbuffer	2020-07-10 08:48:19 +02:00
printk_ringbuffer.c	printk: ringbuffer: fix line counting	2021-01-27 11:55:08 +01:00
printk_ringbuffer.h	printk: avoid and/or handle record truncation	2020-09-30 13:30:28 +02:00
printk_safe.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial	2020-10-15 15:11:56 -07:00
printk.c	printk: fix buffer overflow potential for print_text()	2021-01-30 13:55:20 +01:00