Presently, a core_pattern pipe endpoint will be run in the init namespace. It will receive the virtual pid (task_tgid_vnr->%p) of the core dumping process but will have no access to that processes /proc without walking the init namespace /proc looking through all the global pids until it finds the one it thinks matches.
One option for fixing this is to change the reported pid: https://patchwork.kernel.org/patch/185912/ However, it's unclear if it is desirable for the core_pattern to run outside the namespace. In particular, it can easily access the mounts via /proc/[pid_nr]/root, but if there is a net namespace, it will not have access. (Originally introduced in 2007 in commit b488893a390edfe027bae7a46e9af8083e740668 ) Instead, this change implements the more complex option two. It migrates the ____call_usermodehelper() thread into the same namespaces as the dumping process. It does not assign a pid in that namespace so the collector will appear to be pid 0 in the namespace. Signed-off-by: Will Drewry <[email protected]> --- v2: dropped patch 1/2 removed use of new copy_namespaces_unattached ([email protected]) moved pipe_params into coredump_params ([email protected]) fs/exec.c | 46 +++++++++++++++++++++++++++++++++++++++++++++- include/linux/binfmts.h | 9 +++++++++ 2 files changed, 54 insertions(+), 1 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 828dd24..4cbb735 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -51,6 +51,7 @@ #include <linux/audit.h> #include <linux/tracehook.h> #include <linux/kmod.h> +#include <linux/nsproxy.h> #include <linux/fsnotify.h> #include <linux/fs_struct.h> #include <linux/pipe_fs_i.h> @@ -1820,7 +1821,32 @@ static int umh_pipe_setup(struct subprocess_info *info) struct file *rp, *wp; struct fdtable *fdt; struct coredump_params *cp = (struct coredump_params *)info->data; - struct files_struct *cf = current->files; + struct coredump_pipe_params *pipe_params = &cp->pipe_params; + struct task_struct *tsk = current; + struct files_struct *cf = tsk->files; + struct fs_struct *cfs = tsk->fs; + + /* Migrate this thread into the crashing namespaces, but + * don't change its pid struct to avoid breaking any other + * dependencies. This will mean the process is pid=0 if it + * was migrated into a pid namespace. + */ + if (pipe_params->nsproxy && pipe_params->fs) { + int kill; + switch_task_namespaces(tsk, pipe_params->nsproxy); + pipe_params->nsproxy = NULL; + + task_lock(tsk); + tsk->fs = pipe_params->fs; + task_unlock(tsk); + pipe_params->fs = NULL; + /* Clean up the previous fs struct */ + write_lock(&cfs->lock); + kill = !--cfs->users; + write_unlock(&cfs->lock); + if (kill) + free_fs_struct(cfs); + } wp = create_write_pipe(0); if (IS_ERR(wp)) @@ -1950,10 +1976,28 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs) goto fail_dropcount; } + /* Run the core_collector in the crashing namespaces */ + cprm.pipe_params.fs = copy_fs_struct(current->fs); + if (!cprm.pipe_params.fs) { + printk(KERN_WARNING "%s failed to copy fs\n", + __func__); + argv_free(helper_argv); + goto fail_dropcount; + } + get_nsproxy(current->nsproxy); + cprm.pipe_params.nsproxy = current->nsproxy; + retval = call_usermodehelper_fns(helper_argv[0], helper_argv, NULL, UMH_WAIT_EXEC, umh_pipe_setup, NULL, &cprm); argv_free(helper_argv); + /* nsproxy and fs will survive if call_usermodehelper_fns hits + * ENOMEM prior to creating a new thread. + */ + if (cprm.pipe_params.nsproxy) + put_nsproxy(cprm.pipe_params.nsproxy); + if (cprm.pipe_params.fs) /* not in use by anything else */ + free_fs_struct(cprm.pipe_params.fs); if (retval) { printk(KERN_INFO "Core dump to %s pipe failed\n", corename); diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index a065612..2629603 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -68,6 +68,12 @@ struct linux_binprm{ #define BINPRM_MAX_RECURSION 4 +/* Parameters to be passed to a pipe target during coredump */ +struct coredump_pipe_params { + struct nsproxy *nsproxy; + struct fs_struct *fs; +}; + /* Function parameter for binfmt->coredump */ struct coredump_params { long signr; @@ -75,6 +81,9 @@ struct coredump_params { struct file *file; unsigned long limit; unsigned long mm_flags; + union { + struct coredump_pipe_params pipe_params; + }; }; /* -- 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
