lkml.org 
[lkml]   [2016]   [Mar]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.4 019/342] unix: correctly track in-flight fds in sending process user_struct
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    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: Greg Kroah-Hartman <gregkh@linuxfoundation.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(-)

    --- 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);
    --- 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];
    };

    --- a/net/core/scm.c
    +++ b/net/core/scm.c
    @@ -87,6 +87,7 @@ static int scm_fp_copy(struct cmsghdr *c
    *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 *c
    *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 *sc
    scm->fp = NULL;
    for (i=fpl->count-1; i>=0; i--)
    fput(fpl->fp[i]);
    + free_uid(fpl->user);
    kfree(fpl);
    }
    }
    @@ -336,6 +342,7 @@ struct scm_fp_list *scm_fp_dup(struct sc
    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;
    }
    --- a/net/unix/af_unix.c
    +++ b/net/unix/af_unix.c
    @@ -1496,7 +1496,7 @@ static void unix_detach_fds(struct scm_c
    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)
    @@ -1561,7 +1561,7 @@ static int unix_attach_fds(struct scm_co
    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;
    }

    --- a/net/unix/garbage.c
    +++ b/net/unix/garbage.c
    @@ -116,7 +116,7 @@ struct sock *unix_get_socket(struct file
    * 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);

    @@ -133,11 +133,11 @@ 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);

    @@ -152,7 +152,7 @@ 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);
    }
    \
     
     \ /
      Last update: 2016-03-02 03:21    [W:4.141 / U:0.020 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site