From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Frederic Sowa Subject: Re: [PATCH v2] unix: properly account for FDs passed over unix sockets Date: Tue, 2 Feb 2016 22:55:03 +0100 Message-ID: <56B125B7.6020702@stressinduktion.org> References: <201601100657.u0A6vk1B025554@mail.home.local> <56B0F574.5080105@stressinduktion.org> <56B11278.8000805@stressinduktion.org> <20160202203929.GC25828@1wt.eu> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Linus Torvalds , David Herrmann , "David S. Miller" , netdev , linux-kernel , Eric Dumazet , ???????? ?????????????????? , Tetsuo Handa , Simon McVittie To: Willy Tarreau Return-path: In-Reply-To: <20160202203929.GC25828@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Hi Willy, On 02.02.2016 21:39, Willy Tarreau wrote: > On Tue, Feb 02, 2016 at 09:32:56PM +0100, Hannes Frederic Sowa wrote: >> But "struct pid *" in unix_skb_parms should be enough to get us to >> corresponding "struct cred *" so we can decrement the correct counter >> during skb destruction. >> >> So: >> >> We increment current task's unix_inflight and also check the current >> task's limit during attaching fds to skbs and decrement the inflight >> counter via "struct pid *". This looks like it should work. > > I like it as well, the principle sounds sane. > >>> That way it's always the person who actually does the send (rather >>> than the opener of the socket _or_ the opener of the file that gets >>> passed around) that gets credited, and thanks to the cred pointer we >>> can then de-credit them properly. >> >> Exactly, I try to implement that. Thanks a lot! > > Thanks to you Hannes, I appreciate that you work on it, it would take > much more time to me to dig into this. I slightly tested the attached patch. If you have the original reproducer available could you also give it a try? Unfortunately I currently don't find it and am limited in time this evening. Thanks a lot, Hannes diff --git a/include/net/af_unix.h b/include/net/af_unix.h index 2a91a0561a4783..4567dbe04f274d 100644 --- a/include/net/af_unix.h +++ b/include/net/af_unix.h @@ -6,8 +6,8 @@ #include #include -void unix_inflight(struct file *fp); -void unix_notinflight(struct file *fp); +void unix_inflight(const struct cred *cred, struct file *fp); +void unix_notinflight(const struct cred *cred, struct file *fp); void unix_gc(void); void wait_for_unix_gc(void); struct sock *unix_get_socket(struct file *filp); diff --git a/include/net/scm.h b/include/net/scm.h index 262532d111f51e..8bf7d496545bf8 100644 --- a/include/net/scm.h +++ b/include/net/scm.h @@ -21,6 +21,7 @@ struct scm_creds { struct scm_fp_list { short count; short max; + const struct cred *cred; struct file *fp[SCM_MAX_FD]; }; diff --git a/net/core/scm.c b/net/core/scm.c index 14596fb3717270..6b02b574e283f6 100644 --- a/net/core/scm.c +++ b/net/core/scm.c @@ -87,6 +87,7 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) *fplp = fpl; fpl->count = 0; fpl->max = SCM_MAX_FD; + fpl->cred = NULL; } fpp = &fpl->fp[fpl->count]; @@ -107,6 +108,10 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) *fpp++ = file; fpl->count++; } + + if (fpl->cred) + put_cred(fpl->cred); + fpl->cred = get_current_cred(); return num; } @@ -119,6 +124,7 @@ void __scm_destroy(struct scm_cookie *scm) scm->fp = NULL; for (i=fpl->count-1; i>=0; i--) fput(fpl->fp[i]); + put_cred(fpl->cred); kfree(fpl); } } @@ -336,6 +342,7 @@ struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) for (i = 0; i < fpl->count; i++) get_file(fpl->fp[i]); new_fpl->max = new_fpl->count; + new_fpl->cred = get_cred(fpl->cred); } return new_fpl; } diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 49d5093eb0553a..ba5058682419ba 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1496,7 +1496,7 @@ static void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb) UNIXCB(skb).fp = NULL; for (i = scm->fp->count-1; i >= 0; i--) - unix_notinflight(scm->fp->fp[i]); + unix_notinflight(scm->fp->cred, scm->fp->fp[i]); } static void unix_destruct_scm(struct sk_buff *skb) @@ -1561,7 +1561,7 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb) return -ENOMEM; for (i = scm->fp->count - 1; i >= 0; i--) - unix_inflight(scm->fp->fp[i]); + unix_inflight(scm->fp->cred, scm->fp->fp[i]); return max_level; } diff --git a/net/unix/garbage.c b/net/unix/garbage.c index 8fcdc2283af50c..30b03e7dddd547 100644 --- a/net/unix/garbage.c +++ b/net/unix/garbage.c @@ -116,7 +116,7 @@ struct sock *unix_get_socket(struct file *filp) * descriptor if it is for an AF_UNIX socket. */ -void unix_inflight(struct file *fp) +void unix_inflight(const struct cred *cred, struct file *fp) { struct sock *s = unix_get_socket(fp); @@ -133,11 +133,11 @@ void unix_inflight(struct file *fp) } unix_tot_inflight++; } - fp->f_cred->user->unix_inflight++; + cred->user->unix_inflight++; spin_unlock(&unix_gc_lock); } -void unix_notinflight(struct file *fp) +void unix_notinflight(const struct cred *cred, struct file *fp) { struct sock *s = unix_get_socket(fp); @@ -152,7 +152,7 @@ void unix_notinflight(struct file *fp) list_del_init(&u->link); unix_tot_inflight--; } - fp->f_cred->user->unix_inflight--; + cred->user->unix_inflight--; spin_unlock(&unix_gc_lock); }