linux-kernel - [PATCH V2] fs: don't write pages when receiving a pending SIGKILL in __get_user

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Sat, 18 Jan 2014 09:20:50 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	<robin.yb@...wei.com>, David Rientjes <rientjes@...gle.com>,
	<viro@...iv.linux.org.uk>
CC:	<linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH V2] fs: don't write pages when receiving a pending SIGKILL
 in __get_user_pages()

In the process IO direction, dio_refill_pages will call get_user_pages_fast 
to map the page from user space. If ret is less than 0 and IO is write, the 
function will create a zero page to fill data. This may work for some file 
system, but in some device operate we prefer whole write or fail, not half 
data half zero, e.g. fs metadata, like inode, identy.
This happens often when kill a process which is doing direct IO. Consider 
the following cases, the process A is doing IO process, may enter __get_user_pages 
function, if other processes send process A SIG_KILL, A will enter the 
following branches 
		/*
		 * If we have a pending SIGKILL, don't keep faulting
		 * pages and potentially allocating memory.
		 */
		if (unlikely(fatal_signal_pending(current)))
			return i ? i : -ERESTARTSYS;
Return current pages. direct IO will write the pages, the subsequent pages 
which can’t get will use zero page instead. 

Signed-off-by: Xishi Qiu <qiuxishi@...wei.com>
Signed-off-by: Bin Yang <robin.yb@...wei.com>
---
 fs/direct-io.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 0e04142..b74d565 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -174,6 +174,9 @@ static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
 		&dio->pages[0]);		/* Put results here */
 
 	if (ret < 0 && sdio->blocks_available && (dio->rw & WRITE)) {
+		/* If task is killed, do not write anymore */
+		if (ret == -ERESTARTSYS)
+			goto out;
 		struct page *page = ZERO_PAGE(0);
 		/*
 		 * A memory fault, but the filesystem has some outstanding
-- 
1.7.1



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/