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authorWilly Tarreau <w@1wt.eu>2016-07-15 14:26:27 -0400
committerWilly Tarreau <w@1wt.eu>2016-08-21 23:22:36 +0200
commitf474c525b4f412522cd092b6c8bffb6a0fd9a4de (patch)
tree0717fc838ed66f41a43cfc4f267a9ce2fd8bc5e8 /kernel
parentb1b4becf713431393006d95bbba9b6b3586255f0 (diff)
downloadlwn-f474c525b4f412522cd092b6c8bffb6a0fd9a4de.tar.gz
lwn-f474c525b4f412522cd092b6c8bffb6a0fd9a4de.zip
pipe: limit the per-user amount of pages allocated in pipes
commit 759c01142a5d0f364a462346168a56de28a80f52 upstream. On no-so-small systems, it is possible for a single process to cause an OOM condition by filling large pipes with data that are never read. A typical process filling 4000 pipes with 1 MB of data will use 4 GB of memory. On small systems it may be tricky to set the pipe max size to prevent this from happening. This patch makes it possible to enforce a per-user soft limit above which new pipes will be limited to a single page, effectively limiting them to 4 kB each, as well as a hard limit above which no new pipes may be created for this user. This has the effect of protecting the system against memory abuse without hurting other users, and still allowing pipes to work correctly though with less data at once. The limit are controlled by two new sysctls : pipe-user-pages-soft, and pipe-user-pages-hard. Both may be disabled by setting them to zero. The default soft limit allows the default number of FDs per process (1024) to create pipes of the default size (64kB), thus reaching a limit of 64MB before starting to create only smaller pipes. With 256 processes limited to 1024 FDs each, this results in 1024*64kB + (256*1024 - 1024) * 4kB = 1084 MB of memory allocated for a user. The hard limit is disabled by default to avoid breaking existing applications that make intensive use of pipes (eg: for splicing). CVE-2016-2847 Reported-by: socketpair@gmail.com Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Mitigates: CVE-2013-4312 (Linux 2.0+) Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Willy Tarreau <w@1wt.eu> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> Signed-off-by: Chas Williams <3chas3@gmail.com>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sysctl.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 9469f4c61a30..4fd49fe1046d 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1632,6 +1632,20 @@ static struct ctl_table fs_table[] = {
.proc_handler = &pipe_proc_fn,
.extra1 = &pipe_min_size,
},
+ {
+ .procname = "pipe-user-pages-hard",
+ .data = &pipe_user_pages_hard,
+ .maxlen = sizeof(pipe_user_pages_hard),
+ .mode = 0644,
+ .proc_handler = proc_doulongvec_minmax,
+ },
+ {
+ .procname = "pipe-user-pages-soft",
+ .data = &pipe_user_pages_soft,
+ .maxlen = sizeof(pipe_user_pages_soft),
+ .mode = 0644,
+ .proc_handler = proc_doulongvec_minmax,
+ },
{ }
};