5a814231ae
printk_late_init() is responsible for disabling boot consoles that use init memory. It checks the address of struct console for this. But this is not enough. For example, there are several early consoles that have write() method in the init section and struct console in the normal section. They are not disabled and could cause fancy and hard to debug system states. It is even more complicated by the macros EARLYCON_DECLARE() and OF_EARLYCON_DECLARE() where various struct members are set at runtime by the provided setup() function. I have tried to reproduce this problem and forced the classic uart early console to stay using keep_bootcon parameter. In particular I used earlycon=uart,io,0x3f8 keep_bootcon console=ttyS0,115200. The system did not boot: [ 1.570496] PM: Image not found (code -22) [ 1.570496] PM: Image not found (code -22) [ 1.571886] PM: Hibernation image not present or could not be loaded. [ 1.571886] PM: Hibernation image not present or could not be loaded. [ 1.576407] Freeing unused kernel memory: 2528K [ 1.577244] kernel tried to execute NX-protected page - exploit attempt? (uid: 0) The double lines are caused by having both early uart console and ttyS0 console enabled at the same time. The early console stopped working when the init memory was freed. Fortunately, the invalid call was caught by the NX-protexted page check and did not cause any silent fancy problems. This patch adds a check for many other addresses stored in struct console. It omits setup() and match() that are used only when the console is registered. Therefore they have already been used at this point and there is no reason to use them again. Link: http://lkml.kernel.org/r/1500036673-7122-3-git-send-email-pmladek@suse.com Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Matt Redfearn <matt.redfearn@imgtec.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jiri Slaby <jslaby@suse.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk> Cc: "Fabio M. Di Nitto" <fdinitto@redhat.com> Cc: linux-serial@vger.kernel.org Cc: linux-kernel@vger.kernel.org Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Petr Mladek <pmladek@suse.com> |
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README
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.