path: root/Documentation/sysctl
diff options
authorNeil Horman <nhorman@tuxdriver.com>2009-09-23 15:56:56 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-24 07:21:00 -0700
commita293980c2e261bd5b0d2a77340dd04f684caff58 (patch)
tree69f2b2747548deafb146c18953ebce21ae1f02d4 /Documentation/sysctl
parent725eae32df7754044809973034429a47e6035158 (diff)
exec: let do_coredump() limit the number of concurrent dumps to pipes
Introduce core pipe limiting sysctl. Since we can dump cores to pipe, rather than directly to the filesystem, we create a condition in which a user can create a very high load on the system simply by running bad applications. If the pipe reader specified in core_pattern is poorly written, we can have lots of ourstandig resources and processes in the system. This sysctl introduces an ability to limit that resource consumption. core_pipe_limit defines how many in-flight dumps may be run in parallel, dumps beyond this value are skipped and a note is made in the kernel log. A special value of 0 in core_pipe_limit denotes unlimited core dumps may be handled (this is the default value). [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Neil Horman <nhorman@tuxdriver.com> Reported-by: Earl Chew <earl_chew@agilent.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: Andi Kleen <andi@firstfloor.org> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/sysctl')
1 files changed, 22 insertions, 0 deletions
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index b3d8b492274..a028b92001e 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -22,6 +22,7 @@ show up in /proc/sys/kernel:
- callhome [ S390 only ]
- auto_msgmni
- core_pattern
+- core_pipe_limit
- core_uses_pid
- ctrl-alt-del
- dentry-state
@@ -135,6 +136,27 @@ core_pattern is used to specify a core dumpfile pattern name.
+This sysctl is only applicable when core_pattern is configured to pipe core
+files to user space helper a (when the first character of core_pattern is a '|',
+see above). When collecting cores via a pipe to an application, it is
+occasionally usefull for the collecting application to gather data about the
+crashing process from its /proc/pid directory. In order to do this safely, the
+kernel must wait for the collecting process to exit, so as not to remove the
+crashing processes proc files prematurely. This in turn creates the possibility
+that a misbehaving userspace collecting process can block the reaping of a
+crashed process simply by never exiting. This sysctl defends against that. It
+defines how many concurrent crashing processes may be piped to user space
+applications in parallel. If this value is exceeded, then those crashing
+processes above that value are noted via the kernel log and their cores are
+skipped. 0 is a special value, indicating that unlimited processes may be
+captured in parallel, but that no waiting will take place (i.e. the collecting
+process is not guaranteed access to /proc/<crahing pid>/). This value defaults
+to 0.
The default coredump filename is "core". By setting