From f8d570a4745835f2238a33b537218a1bb03fc671 Mon Sep 17 00:00:00 2001 From: David Miller Date: Thu, 6 Nov 2008 00:37:40 -0800 Subject: [PATCH] net: Fix recursive descent in __scm_destroy(). __scm_destroy() walks the list of file descriptors in the scm_fp_list pointed to by the scm_cookie argument. Those, in turn, can close sockets and invoke __scm_destroy() again. There is nothing which limits how deeply this can occur. The idea for how to fix this is from Linus. Basically, we do all of the fput()s at the top level by collecting all of the scm_fp_list objects hit by an fput(). Inside of the initial __scm_destroy() we keep running the list until it is empty. Signed-off-by: David S. Miller Signed-off-by: Linus Torvalds --- include/linux/sched.h | 2 ++ include/net/scm.h | 5 +++-- net/core/scm.c | 24 +++++++++++++++++++++--- 3 files changed, 26 insertions(+), 5 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index b483f39a711..295b7c756ca 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1349,6 +1349,8 @@ struct task_struct { */ unsigned long timer_slack_ns; unsigned long default_timer_slack_ns; + + struct list_head *scm_work_list; }; /* diff --git a/include/net/scm.h b/include/net/scm.h index 06df126103c..33e9986beb8 100644 --- a/include/net/scm.h +++ b/include/net/scm.h @@ -14,8 +14,9 @@ struct scm_fp_list { - int count; - struct file *fp[SCM_MAX_FD]; + struct list_head list; + int count; + struct file *fp[SCM_MAX_FD]; }; struct scm_cookie diff --git a/net/core/scm.c b/net/core/scm.c index 10f5c65f6a4..ab242cc1acc 100644 --- a/net/core/scm.c +++ b/net/core/scm.c @@ -75,6 +75,7 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) if (!fpl) return -ENOMEM; *fplp = fpl; + INIT_LIST_HEAD(&fpl->list); fpl->count = 0; } fpp = &fpl->fp[fpl->count]; @@ -106,9 +107,25 @@ void __scm_destroy(struct scm_cookie *scm) if (fpl) { scm->fp = NULL; - for (i=fpl->count-1; i>=0; i--) - fput(fpl->fp[i]); - kfree(fpl); + if (current->scm_work_list) { + list_add_tail(&fpl->list, current->scm_work_list); + } else { + LIST_HEAD(work_list); + + current->scm_work_list = &work_list; + + list_add(&fpl->list, &work_list); + while (!list_empty(&work_list)) { + fpl = list_first_entry(&work_list, struct scm_fp_list, list); + + list_del(&fpl->list); + for (i=fpl->count-1; i>=0; i--) + fput(fpl->fp[i]); + kfree(fpl); + } + + current->scm_work_list = NULL; + } } } @@ -284,6 +301,7 @@ struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) new_fpl = kmalloc(sizeof(*fpl), GFP_KERNEL); if (new_fpl) { + INIT_LIST_HEAD(&new_fpl->list); for (i=fpl->count-1; i>=0; i--) get_file(fpl->fp[i]); memcpy(new_fpl, fpl, sizeof(*fpl)); -- 2.39.3