On Fri, 14 Dec 2012 16:04:08 -0500 Neil Horman <nhor...@tuxdriver.com> wrote:
> As its currently implemented, redirection of core dumps to a pipe reader > should > be executed such that the reader runs in the namespace of the crashing > process, > and it currently does not. This is the only sane way to deal with namespaces > properly it seems to me, and this patch implements that functionality. > > Theres one problem I currently see with it, and that is that I'm not sure we > can > change the current behavior of how the root fs is set for the pipe reader, > lest > we break some user space expectations. As such I've made the switching of > namespaces configurable based on the addition of an extra '|' token in the > core_pattern sysctl. 1 '|' indicates a pipe using the global namespace, while > 2 '|' indicates that the namespace and root of the crashing process should be > used. > > I've tested this using both settings for the new sysctl, and it works well. > > For the sake of history, this was discussed before: > http://www.spinics.net/lists/linux-containers/msg21531.html > > It seems there was some modicum of consensus as to how this should work, but > there was no action taken on it. > > --- a/fs/coredump.c > +++ b/fs/coredump.c > @@ -164,6 +164,18 @@ static int format_corename(struct core_name *cn, struct > coredump_params *cprm) > if (!cn->corename) > return -ENOMEM; > > + if (ispipe) { > + /* > + * If we have 2 | tokens at the head of core_pattern, it > + * indicates we are a pipe and the reader should inherit the > + * namespaces of the crashing process > + */ > + cprm->switch_ns = (*(pat_ptr+1) == '|') ? true : false; > + if (cprm->switch_ns) > + /* Advance pat_ptr so as not to mess up corename */ > + pat_ptr++; > + } > + That was, umm, intricate. How's about this? if (ispipe && pat_ptr[1] == '|') { /* * We have 2 | tokens at the head of core_pattern which * indicates we are a pipe and the reader should inherit the * namespaces of the crashing process */ cprm->switch_ns = true; pat_ptr++; } --- a/Documentation/sysctl/kernel.txt~core_pattern-set-core-helpers-root-and-namespace-to-crashing-process-fix +++ a/Documentation/sysctl/kernel.txt @@ -194,7 +194,7 @@ core_pattern is used to specify a core d written to the standard input of that program instead of to a file. Note that when using |, the core pipe reader that is executed will be run in the global namespace and root filesystem. If two | tokens (i.e. ||) are supplied as the - first two characters of the core_pattern sysctl, the kernel will preform the + first two characters of the core_pattern sysctl, the kernel will perform the same pipe operation, but the core pipe reader will be executed using the namespace and root fs of the crashing process. --- a/fs/coredump.c~core_pattern-set-core-helpers-root-and-namespace-to-crashing-process-fix +++ a/fs/coredump.c @@ -164,16 +164,14 @@ static int format_corename(struct core_n if (!cn->corename) return -ENOMEM; - if (ispipe) { + if (ispipe && pat_ptr[1] == '|') { /* - * If we have 2 | tokens at the head of core_pattern, it + * We have 2 | tokens at the head of core_pattern which * indicates we are a pipe and the reader should inherit the * namespaces of the crashing process */ - cprm->switch_ns = (*(pat_ptr+1) == '|') ? true : false; - if (cprm->switch_ns) - /* Advance pat_ptr so as not to mess up corename */ - pat_ptr++; + cprm->switch_ns = true; + pat_ptr++; } /* Repeat as long as we have more pattern to process and more output _ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
