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authorHannes Frederic Sowa <hannes@stressinduktion.org>2016-02-03 02:11:03 +0100
committerBen Hutchings <ben@decadent.org.uk>2016-02-27 14:28:49 +0000
commit5ea820046ee399214221c0bb817eb35d304c9604 (patch)
treeb80a7bdd2a43cb841f0a3015c39f636282e9f190
parenta5a6cf8c405e826ff7ed1308dde72560c0ed4854 (diff)
downloadlwn-5ea820046ee399214221c0bb817eb35d304c9604.tar.gz
lwn-5ea820046ee399214221c0bb817eb35d304c9604.zip
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 <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> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
-rw-r--r--include/net/af_unix.h4
-rw-r--r--include/net/scm.h1
-rw-r--r--net/core/scm.c7
-rw-r--r--net/unix/af_unix.c4
-rw-r--r--net/unix/garbage.c8
5 files changed, 16 insertions, 8 deletions
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 <linux/mutex.h>
#include <net/sock.h>
-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);
}