From: Hannes Frederic Sowa hannes@stressinduktion.org
[ Upstream commit 415e3d3e90ce9e18727e8843ae343eda5a58fad6 ]
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 dh.herrmann@gmail.com Cc: David Herrmann dh.herrmann@gmail.com Cc: Willy Tarreau w@1wt.eu Cc: Linus Torvalds torvalds@linux-foundation.org Suggested-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Hannes Frederic Sowa hannes@stressinduktion.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/af_unix.h | 4 ++-- include/net/scm.h | 1 + net/core/scm.c | 7 +++++++ net/unix/af_unix.c | 4 ++-- net/unix/garbage.c | 8 ++++---- 5 files changed, 16 insertions(+), 8 deletions(-)
diff --git a/include/net/af_unix.h b/include/net/af_unix.h index e830c3dff61a..7bb69c9c3c43 100644 --- a/include/net/af_unix.h +++ b/include/net/af_unix.h @@ -6,8 +6,8 @@ #include <linux/mutex.h> #include <net/sock.h>
-void unix_inflight(struct file *fp); -void unix_notinflight(struct file *fp); +void unix_inflight(struct user_struct *user, struct file *fp); +void unix_notinflight(struct user_struct *user, 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 262532d111f5..59fa93c01d2a 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; + struct user_struct *user; struct file *fp[SCM_MAX_FD]; };
diff --git a/net/core/scm.c b/net/core/scm.c index d30eb057fa7b..cad57a1390dd 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->user = 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->user) + fpl->user = get_uid(current_user()); + 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]); + free_uid(fpl->user); kfree(fpl); } } @@ -337,6 +343,7 @@ 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 29b1f4dc48ca..1bd4ba6b6aa4 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1469,7 +1469,7 @@ 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) @@ -1534,7 +1534,7 @@ 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 58783dcfd35d..1105a60468ac 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);
@@ -139,11 +139,11 @@ 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);
@@ -158,7 +158,7 @@ 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); }