• Takeshi Misawa's avatar
    ppp: Fix memory leak in ppp_write · 4c247de5
    Takeshi Misawa authored
    When ppp is closing, __ppp_xmit_process() failed to enqueue skb
    and skb allocated in ppp_write() is leaked.
    
    syzbot reported :
    BUG: memory leak
    unreferenced object 0xffff88812a17bc00 (size 224):
      comm "syz-executor673", pid 6952, jiffies 4294942888 (age 13.040s)
      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:
        [<00000000d110fff9>] kmemleak_alloc_recursive include/linux/kmemleak.h:43 [inline]
        [<00000000d110fff9>] slab_post_alloc_hook mm/slab.h:522 [inline]
        [<00000000d110fff9>] slab_alloc_node mm/slab.c:3262 [inline]
        [<00000000d110fff9>] kmem_cache_alloc_node+0x163/0x2f0 mm/slab.c:3574
        [<000000002d616113>] __alloc_skb+0x6e/0x210 net/core/skbuff.c:197
        [<000000000167fc45>] alloc_skb include/linux/skbuff.h:1055 [inline]
        [<000000000167fc45>] ppp_write+0x48/0x120 drivers/net/ppp/ppp_generic.c:502
        [<000000009ab42c0b>] __vfs_write+0x43/0xa0 fs/read_write.c:494
        [<00000000086b2e22>] vfs_write fs/read_write.c:558 [inline]
        [<00000000086b2e22>] vfs_write+0xee/0x210 fs/read_write.c:542
        [<00000000a2b70ef9>] ksys_write+0x7c/0x130 fs/read_write.c:611
        [<00000000ce5e0fdd>] __do_sys_write fs/read_write.c:623 [inline]
        [<00000000ce5e0fdd>] __se_sys_write fs/read_write.c:620 [inline]
        [<00000000ce5e0fdd>] __x64_sys_write+0x1e/0x30 fs/read_write.c:620
        [<00000000d9d7b370>] do_syscall_64+0x76/0x1a0 arch/x86/entry/common.c:296
        [<0000000006e6d506>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
    
    Fix this by freeing skb, if ppp is closing.
    
    Fixes: 6d066734
    
     ("ppp: avoid loop in xmit recursion detection code")
    Reported-and-tested-by: syzbot+d9c8bf24e56416d7ce2c@syzkaller.appspotmail.com
    Signed-off-by: default avatarTakeshi Misawa <jeliantsurux@gmail.com>
    Reviewed-by: default avatarGuillaume Nault <gnault@redhat.com>
    Tested-by: default avatarGuillaume Nault <gnault@redhat.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    4c247de5