Re: [syzbot] memory leak in ip_vs_add_service

[Xin Long]

On Mon, May 24, 2021 at 10:33 AM syzbot
<syzbot+e562383183e4b1766930@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    c3d0e3fd Merge tag 'fs.idmapped.mount_setattr.v5.13-rc3' o..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=148d0bd7d00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=ae7b129a135ab06b
> dashboard link: https://syzkaller.appspot.com/bug?extid=e562383183e4b1766930
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15585a4bd00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13900753d00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+e562383183e4b1766930@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> BUG: memory leak
> unreferenced object 0xffff888115227800 (size 512):
>   comm "syz-executor263", pid 8658, jiffies 4294951882 (age 12.560s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffff83977188>] kmalloc include/linux/slab.h:556 [inline]
>     [<ffffffff83977188>] kzalloc include/linux/slab.h:686 [inline]
>     [<ffffffff83977188>] ip_vs_add_service+0x598/0x7c0 net/netfilter/ipvs/ip_vs_ctl.c:1343
>     [<ffffffff8397d770>] do_ip_vs_set_ctl+0x810/0xa40 net/netfilter/ipvs/ip_vs_ctl.c:2570
>     [<ffffffff838449a8>] nf_setsockopt+0x68/0xa0 net/netfilter/nf_sockopt.c:101
>     [<ffffffff839ae4e9>] ip_setsockopt+0x259/0x1ff0 net/ipv4/ip_sockglue.c:1435
>     [<ffffffff839fa03c>] raw_setsockopt+0x18c/0x1b0 net/ipv4/raw.c:857
>     [<ffffffff83691f20>] __sys_setsockopt+0x1b0/0x360 net/socket.c:2117
>     [<ffffffff836920f2>] __do_sys_setsockopt net/socket.c:2128 [inline]
>     [<ffffffff836920f2>] __se_sys_setsockopt net/socket.c:2125 [inline]
>     [<ffffffff836920f2>] __x64_sys_setsockopt+0x22/0x30 net/socket.c:2125
>     [<ffffffff84350efa>] do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
>     [<ffffffff84400068>] entry_SYSCALL_64_after_hwframe+0x44/0xae
do_ip_vs_set_ctl() allows users to add svc with the flags field set.
when IP_VS_SVC_F_HASHED is used, and in ip_vs_svc_hash()
called ip_vs_add_service() will trigger the err msg:

IPVS: ip_vs_svc_hash(): request for already hashed, called from
do_ip_vs_set_ctl+0x810/0xa40

and the svc allocated will leak.

so fix it by mask the flags with ~IP_VS_SVC_F_HASHED in
ip_vs_copy_usvc_compat(), while at it also remove the unnecessary
flag IP_VS_SVC_F_HASHED set in ip_vs_edit_service().

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index d45dbcba8b49..f09a443c9ec0 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -1497,7 +1497,6 @@ ip_vs_edit_service(struct ip_vs_service *svc,
struct ip_vs_service_user_kern *u)
        /*
         * Set the flags and timeout value
         */
-       svc->flags = u->flags | IP_VS_SVC_F_HASHED;
        svc->timeout = u->timeout * HZ;
        svc->netmask = u->netmask;

@@ -2430,7 +2429,7 @@ static void ip_vs_copy_usvc_compat(struct
ip_vs_service_user_kern *usvc,
        /* Deep copy of sched_name is not needed here */
        usvc->sched_name        = usvc_compat->sched_name;

-       usvc->flags             = usvc_compat->flags;
+       usvc->flags             = usvc_compat->flags & ~IP_VS_SVC_F_HASHED;
        usvc->timeout           = usvc_compat->timeout;
        usvc->netmask           = usvc_compat->netmask;
 }


>
>
>
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