format_corename uses task_tgid_vnr to provide the numeric pid of a core-dumping process. For file-based coredumps, this is perfectly satisfactory. However, when the core_pattern contains a pipe, the substituted PID is invalid in the namespace of the core_pattern pipe helper, the init namespace.
By changing this, any core collector may now find the process in the init namespace /proc. This helps with VFS namespacing too since the mount root is available via /proc. Unfortunately, it does not help in cases of more complex namespacing, like net namespaces. For that, the helper thread will need to be migrated to the core-dump namespaces. I have a separate patch series which implements migrating the ____call_usermodehelper thread to the coredump namespace, but it adds a fair amount of complexity which might be better handled by someone who understands that code. I'm happy to mail it out as well though (it works, but I don't assign a namespaced pid which may open up issues on its own). Any and all comments, feedback will be appreciated! Signed-off-by: Will Drewry <[email protected]> --- fs/exec.c | 11 +++++++++-- 1 files changed, 9 insertions(+), 2 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 828dd24..0b8a874 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1467,6 +1467,13 @@ static int format_corename(char *corename, long signr) char *const out_end = corename + CORENAME_MAX_SIZE; int rc; int pid_in_pattern = 0; + pid_t pid = task_tgid_vnr(current); + + /* The pipe helper runs in the init namespace and should + * receive the matching pid until that changes. + */ + if (ispipe) + pid = task_tgid_nr(current); /* Repeat as long as we have more pattern to process and more output space */ @@ -1489,7 +1496,7 @@ static int format_corename(char *corename, long signr) case 'p': pid_in_pattern = 1; rc = snprintf(out_ptr, out_end - out_ptr, - "%d", task_tgid_vnr(current)); + "%d", pid); if (rc > out_end - out_ptr) goto out; out_ptr += rc; @@ -1568,7 +1575,7 @@ static int format_corename(char *corename, long signr) * the filename. Do not do this for piped commands. */ if (!ispipe && !pid_in_pattern && core_uses_pid) { rc = snprintf(out_ptr, out_end - out_ptr, - ".%d", task_tgid_vnr(current)); + ".%d", pid); if (rc > out_end - out_ptr) goto out; out_ptr += rc; -- 1.7.0.4 _______________________________________________ Containers mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/containers _______________________________________________ Devel mailing list [email protected] https://openvz.org/mailman/listinfo/devel
