| Message ID | a02c6e7e3135473d254ac97abc603d963ba8f716.1659862577.git.peilin.ye@bytedance.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net,v2,1/2] vsock: Fix memory leak in vsock_connect() | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Clearly marked for net |
| netdev/fixes_present | success | Fixes tag present in non-next series |
| netdev/subject_prefix | success | Link |
| netdev/cover_letter | success | Single patches do not need cover letters |
| netdev/patch_count | success | Link |
| netdev/header_inline | success | No static functions without inline keyword in header files |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/cc_maintainers | success | CCed 10 of 10 maintainers |
| netdev/build_clang | success | Errors and warnings before: 0 this patch: 0 |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Signed-off-by tag matches author and committer |
| netdev/check_selftest | success | No net selftest shell script |
| netdev/verify_fixes | success | Fixes tag looks correct |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/checkpatch | warning | WARNING: line length of 85 exceeds 80 columns |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/source_inline | success | Was 0 now: 0 |
On Sun, Aug 07, 2022 at 02:00:11AM -0700, Peilin Ye wrote: >From: Peilin Ye <peilin.ye@bytedance.com> > >An O_NONBLOCK vsock_connect() request may try to reschedule >@connect_work. Imagine the following sequence of vsock_connect() >requests: > > 1. The 1st, non-blocking request schedules @connect_work, which will > expire after 200 jiffies. Socket state is now SS_CONNECTING; > > 2. Later, the 2nd, blocking request gets interrupted by a signal after > a few jiffies while waiting for the connection to be established. > Socket state is back to SS_UNCONNECTED, but @connect_work is still > pending, and will expire after 100 jiffies. > > 3. Now, the 3rd, non-blocking request tries to schedule @connect_work > again. Since @connect_work is already scheduled, > schedule_delayed_work() silently returns. sock_hold() is called > twice, but sock_put() will only be called once in > vsock_connect_timeout(), causing a memory leak reported by syzbot: > > BUG: memory leak > unreferenced object 0xffff88810ea56a40 (size 1232): > comm "syz-executor756", pid 3604, jiffies 4294947681 (age 12.350s) > hex dump (first 32 bytes): > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 28 00 07 40 00 00 00 00 00 00 00 00 00 00 00 00 (..@............ > backtrace: > [<ffffffff837c830e>] sk_prot_alloc+0x3e/0x1b0 net/core/sock.c:1930 > [<ffffffff837cbe22>] sk_alloc+0x32/0x2e0 net/core/sock.c:1989 > [<ffffffff842ccf68>] __vsock_create.constprop.0+0x38/0x320 net/vmw_vsock/af_vsock.c:734 > [<ffffffff842ce8f1>] vsock_create+0xc1/0x2d0 net/vmw_vsock/af_vsock.c:2203 > [<ffffffff837c0cbb>] __sock_create+0x1ab/0x2b0 net/socket.c:1468 > [<ffffffff837c3acf>] sock_create net/socket.c:1519 [inline] > [<ffffffff837c3acf>] __sys_socket+0x6f/0x140 net/socket.c:1561 > [<ffffffff837c3bba>] __do_sys_socket net/socket.c:1570 [inline] > [<ffffffff837c3bba>] __se_sys_socket net/socket.c:1568 [inline] > [<ffffffff837c3bba>] __x64_sys_socket+0x1a/0x20 net/socket.c:1568 > [<ffffffff84512815>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] > [<ffffffff84512815>] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80 > [<ffffffff84600068>] entry_SYSCALL_64_after_hwframe+0x44/0xae > <...> > >Use mod_delayed_work() instead: if @connect_work is already scheduled, >reschedule it, and undo sock_hold() to keep the reference count >balanced. > >Reported-and-tested-by: syzbot+b03f55bf128f9a38f064@syzkaller.appspotmail.com >Fixes: d021c344051a ("VSOCK: Introduce VM Sockets") >Co-developed-by: Stefano Garzarella <sgarzare@redhat.com> >Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> >Signed-off-by: Peilin Ye <peilin.ye@bytedance.com> >--- >change since v1: > - merged with Stefano's patch [1] > >[1] https://gitlab.com/sgarzarella/linux/-/commit/2d0f0b9cbbb30d58fdcbca7c1a857fd8f3110d61 > >Hi Stefano, > >About the Fixes: tag, [2] introduced @connect_work, but all it did was >breaking @dwork into two and moving some INIT_DELAYED_WORK()'s, so I don't >think [2] introduced this memory leak? > >Since [2] has already been backported to 4.9 and 4.14, I think we can >Fixes: commit d021c344051a ("VSOCK: Introduce VM Sockets"), too, to make >backporting easier? Yep, I think it should be fine! > >[2] commit 455f05ecd2b2 ("vsock: split dwork to avoid reinitializations") > >Thanks, >Peilin Ye > > net/vmw_vsock/af_vsock.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > >diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c >index f04abf662ec6..fe14f6cbca22 100644 >--- a/net/vmw_vsock/af_vsock.c >+++ b/net/vmw_vsock/af_vsock.c >@@ -1391,7 +1391,13 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr, > * timeout fires. > */ > sock_hold(sk); >- schedule_delayed_work(&vsk->connect_work, timeout); >+ >+ /* If the timeout function is already scheduled, >+ * reschedule it, then ungrab the socket refcount to >+ * keep it balanced. >+ */ >+ if (mod_delayed_work(system_wq, &vsk->connect_work, timeout)) ^ Checkpatch warns here about line lenght. If you have to re-send, please split it. Anyway, the patch LGTM: Reviewed-by: Stefano Garzarella <sgarzare@redhat.com> Thanks, Stefano
On Mon, Aug 08, 2022 at 09:55:33AM +0200, Stefano Garzarella wrote: > On Sun, Aug 07, 2022 at 02:00:11AM -0700, Peilin Ye wrote: > > net/vmw_vsock/af_vsock.c | 8 +++++++- > > 1 file changed, 7 insertions(+), 1 deletion(-) > > > > diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c > > index f04abf662ec6..fe14f6cbca22 100644 > > --- a/net/vmw_vsock/af_vsock.c > > +++ b/net/vmw_vsock/af_vsock.c > > @@ -1391,7 +1391,13 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr, > > * timeout fires. > > */ > > sock_hold(sk); > > - schedule_delayed_work(&vsk->connect_work, timeout); > > + > > + /* If the timeout function is already scheduled, > > + * reschedule it, then ungrab the socket refcount to > > + * keep it balanced. > > + */ > > + if (mod_delayed_work(system_wq, &vsk->connect_work, timeout)) > ^ > Checkpatch warns here about line lenght. > If you have to re-send, please split it. Oh, net-next HEAD's checkpatch --strict didn't complain, I didn't know Patchwork checks 80 columns. I will send v3 soon. > Anyway, the patch LGTM: > > Reviewed-by: Stefano Garzarella <sgarzare@redhat.com> Thanks! Peilin Ye
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c index f04abf662ec6..fe14f6cbca22 100644 --- a/net/vmw_vsock/af_vsock.c +++ b/net/vmw_vsock/af_vsock.c @@ -1391,7 +1391,13 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr, * timeout fires. */ sock_hold(sk); - schedule_delayed_work(&vsk->connect_work, timeout); + + /* If the timeout function is already scheduled, + * reschedule it, then ungrab the socket refcount to + * keep it balanced. + */ + if (mod_delayed_work(system_wq, &vsk->connect_work, timeout)) + sock_put(sk); /* Skip ahead to preserve error code set above. */ goto out_wait;