From: Hannes Frederic Sowa Date: Wed, 3 Feb 2016 01:11:03 +0000 (+0100) Subject: unix: correctly track in-flight fds in sending process user_struct X-Git-Tag: v3.2.78~5 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5ea820046ee399214221c0bb817eb35d304c9604;p=pandora-kernel.git unix: correctly track in-flight fds in sending process user_struct commit 415e3d3e90ce9e18727e8843ae343eda5a58fad6 upstream. The commit referenced in the Fixes tag incorrectly accounted the number of in-flight fds over a unix domain socket to the original opener of the file-descriptor. This allows another process to arbitrary deplete the original file-openers resource limit for the maximum of open files. Instead the sending processes and its struct cred should be credited. To do so, we add a reference counted struct user_struct pointer to the scm_fp_list and use it to account for the number of inflight unix fds. Fixes: 712f4aad406bb1 ("unix: properly account for FDs passed over unix sockets") Reported-by: David Herrmann Cc: David Herrmann Cc: Willy Tarreau Cc: Linus Torvalds Suggested-by: Linus Torvalds Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- diff --git a/include/net/af_unix.h b/include/net/af_unix.h index f4842f7afaa5..a69bfee1dd27 100644 --- a/include/net/af_unix.h +++ b/include/net/af_unix.h @@ -6,8 +6,8 @@ #include #include -extern void unix_inflight(struct file *fp); -extern void unix_notinflight(struct file *fp); +extern void unix_inflight(struct user_struct *user, struct file *fp); +extern void unix_notinflight(struct user_struct *user, struct file *fp); extern void unix_gc(void); extern void wait_for_unix_gc(void); extern struct sock *unix_get_socket(struct file *filp); diff --git a/include/net/scm.h b/include/net/scm.h index 5da0a7b7eb41..9822a68ae148 100644 --- a/include/net/scm.h +++ b/include/net/scm.h @@ -16,6 +16,7 @@ struct scm_fp_list { struct list_head list; short count; short max; + struct user_struct *user; struct file *fp[SCM_MAX_FD]; }; diff --git a/net/core/scm.c b/net/core/scm.c index 51b4d52a6f98..9adabedaf8ad 100644 --- a/net/core/scm.c +++ b/net/core/scm.c @@ -80,6 +80,7 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) *fplp = fpl; fpl->count = 0; fpl->max = SCM_MAX_FD; + fpl->user = NULL; } fpp = &fpl->fp[fpl->count]; @@ -100,6 +101,10 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) *fpp++ = file; fpl->count++; } + + if (!fpl->user) + fpl->user = get_uid(current_user()); + return num; } @@ -124,6 +129,7 @@ void __scm_destroy(struct scm_cookie *scm) list_del(&fpl->list); for (i=fpl->count-1; i>=0; i--) fput(fpl->fp[i]); + free_uid(fpl->user); kfree(fpl); } @@ -342,6 +348,7 @@ 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->user = get_uid(fpl->user); } return new_fpl; } diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 6798b3cd9776..390e079913f4 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1454,7 +1454,7 @@ 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->user, scm->fp->fp[i]); } static void unix_destruct_scm(struct sk_buff *skb) @@ -1520,7 +1520,7 @@ 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->user, scm->fp->fp[i]); return max_level; } diff --git a/net/unix/garbage.c b/net/unix/garbage.c index fd1a840f5651..33a21260b79b 100644 --- a/net/unix/garbage.c +++ b/net/unix/garbage.c @@ -122,7 +122,7 @@ 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(struct user_struct *user, struct file *fp) { struct sock *s = unix_get_socket(fp); @@ -138,11 +138,11 @@ void unix_inflight(struct file *fp) } unix_tot_inflight++; } - fp->f_cred->user->unix_inflight++; + user->unix_inflight++; spin_unlock(&unix_gc_lock); } -void unix_notinflight(struct file *fp) +void unix_notinflight(struct user_struct *user, struct file *fp) { struct sock *s = unix_get_socket(fp); @@ -155,7 +155,7 @@ void unix_notinflight(struct file *fp) list_del_init(&u->link); unix_tot_inflight--; } - fp->f_cred->user->unix_inflight--; + user->unix_inflight--; spin_unlock(&unix_gc_lock); }