Package: pam Version: 1.1.8-3.1 Severity: important Tags: patch User: ubuntu-de...@lists.ubuntu.com Usertags: origin-ubuntu vivid ubuntu-patch
In Ubuntu, the attached patch was applied to achieve the following:
* d/applied-patches/pam-limits-nofile-fd-setsize-cap: cap the default
soft nofile limit read from pid 1 to FD_SETSIZE.
Debian should probably follow along, unless it wants to risk increasing
the default nofile soft limit beyond FD_SETSIZE. Explanation in the
patch description below.
Thanks for considering the patch.
diff -u pam-1.1.8/debian/patches-applied/series
pam-1.1.8/debian/patches-applied/series
--- pam-1.1.8/debian/patches-applied/series
+++ pam-1.1.8/debian/patches-applied/series
@@ -31 +31 @@
-
+pam-limits-nofile-fd-setsize-cap
only in patch2:
unchanged:
--- pam-1.1.8.orig/debian/patches-applied/pam-limits-nofile-fd-setsize-cap
+++ pam-1.1.8/debian/patches-applied/pam-limits-nofile-fd-setsize-cap
@@ -0,0 +1,58 @@
+From: Robie Basak <robie.ba...@ubuntu.com>
+Subject: pam_limits: cap the default soft nofile limit read from pid 1 to
FD_SETSIZE
+
+Cap the default soft nofile limit read from pid 1 to FD_SETSIZE since
+larger values can cause problems with fd_set overflow and systemd sets
+itself higher.
+
+See:
+https://lists.ubuntu.com/archives/ubuntu-devel/2010-September/031446.html
+http://www.outflux.net/blog/archives/2014/06/13/5-year-old-glibc-select-weakness-fixed/
+https://sourceware.org/bugzilla/show_bug.cgi?id=10352
+https://github.com/systemd/systemd/commit/4096d6f5879aef73e20dd7b62a01f447629945b0
+
+pam_limits reads the default limits from /proc/1/limits. Previously,
+using upstart, this resulted in a 1024 nofile soft limit on Ubuntu
+systems by default. Using systemd, this results in a limit of 65536
+instead. This is not the intention of systemd upstream. See systemd
+commit 4096d6f for an explanation of systemd's behaviour.
+
+If we want to make such a change to the default distribution soft limit
+in PAM, we should do it deliberately and carefully, not accidentally. A
+change should consider what uses select(2) and might inadvertently (and
+incorrectly) assume that file descriptors will always fit into an
+fd_set, what vulnerabilities or crashes the change could consequently
+create, and whether the protection now present with FORTIFY_SOURCE is
+suitably enabled in all relevant builds.
+
+So this keeps the soft limit at 1024 for now. The hard limit will rise
+to 65536 along with systemd. Anything that knows that it will not be
+buggy with respect to fd_set and FD_SETSIZE, such as by using poll(2) or
+epoll(7) instead of select(2), can always raise the soft limit itself
+without issue.
+
+20:54 <rbasak> slangasek: [...] I'm also not sure how to go about
+upstreaming this as pam_limits seems to be heavily patched already.
+
+Forwarded: no
+Reviewed-by: Adam Conrad <adcon...@ubuntu.com>
+Reviewed-by: Martin Pitt <martin.p...@ubuntu.com>
+Last-Update: 2015-04-22
+
+--- a/modules/pam_limits/pam_limits.c
++++ b/modules/pam_limits/pam_limits.c
+@@ -439,6 +439,14 @@ static void parse_kernel_limits(pam_hand
+ pl->limits[i].src_hard = LIMITS_DEF_KERNEL;
+ }
+ fclose(limitsfile);
++
++ /* Cap the default soft nofile limit read from pid 1 to FD_SETSIZE
++ * since larger values can cause problems with fd_set overflow and
++ * systemd sets itself higher. */
++ if (pl->limits[RLIMIT_NOFILE].src_soft == LIMITS_DEF_KERNEL &&
++ pl->limits[RLIMIT_NOFILE].limit.rlim_cur > FD_SETSIZE) {
++ pl->limits[RLIMIT_NOFILE].limit.rlim_cur = FD_SETSIZE;
++ }
+ }
+
+ static int init_limits(pam_handle_t *pamh, struct pam_limit_s *pl, int ctrl)
-- System Information:
Debian Release: jessie/sid
APT prefers vivid-updates
APT policy: (500, 'vivid-updates'), (500, 'vivid-security'), (500, 'vivid')
Architecture: amd64 (x86_64)
Foreign Architectures: i386
Kernel: Linux 3.19.0-12-generic (SMP w/4 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
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