From f8d570a4745835f2238a33b537218a1bb03fc671 Mon Sep 17 00:00:00 2001 From: David Miller Date: Thu, 6 Nov 2008 00:37:40 -0800 Subject: 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 --- net/core/scm.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) (limited to 'net/core/scm.c') diff --git a/net/core/scm.c b/net/core/scm.c index 10f5c65f6a47..ab242cc1acca 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)); -- cgit v1.2.3 From 5421ae0153b4ba0469967cfd8de96144e3bf3979 Mon Sep 17 00:00:00 2001 From: Pavel Emelyanov Date: Fri, 14 Nov 2008 14:51:45 -0800 Subject: scm: fix scm_fp_list->list initialization made in wrong place This is the next page of the scm recursion story (the commit f8d570a4 net: Fix recursive descent in __scm_destroy()). In function scm_fp_dup(), the INIT_LIST_HEAD(&fpl->list) of newly created fpl is done *before* the subsequent memcpy from the old structure and thus the freshly initialized list is overwritten. But that's OK, since this initialization is not required at all, since the fpl->list is list_add-ed at the destruction time in any case (and is unused in other code), so I propose to drop both initializations, rather than moving it after the memcpy. Please, correct me if I miss something significant. Signed-off-by: Pavel Emelyanov Signed-off-by: David S. Miller --- net/core/scm.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'net/core/scm.c') diff --git a/net/core/scm.c b/net/core/scm.c index ab242cc1acca..b12303dd39d9 100644 --- a/net/core/scm.c +++ b/net/core/scm.c @@ -75,7 +75,6 @@ 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]; @@ -301,7 +300,6 @@ 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)); -- cgit v1.2.3