From mboxrd@z Thu Jan 1 00:00:00 1970 From: walter harms Date: Sat, 14 Sep 2019 10:36:05 +0000 Subject: Re: [PATCH] ppp: Fix memory leak in ppp_write Message-Id: <5D7CC295.3090402@bfs.de> List-Id: References: <20190914040958.GA2363@DESKTOP> In-Reply-To: <20190914040958.GA2363@DESKTOP> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ppp@vger.kernel.org Am 14.09.2019 06:09, schrieb Takeshi Misawa: > 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. > > Reported-and-tested-by: syzbot+d9c8bf24e56416d7ce2c@syzkaller.appspotmail.com > Signed-off-by: Takeshi Misawa > --- > Dear Paul Mackerras > > syzbot reported memory leak in net/ppp. > [TITLE] memory leak in ppp_write > > I send a patch that passed syzbot reproducer test. > Please consider this memory leak and patch. > > Regards. > --- > drivers/net/ppp/ppp_generic.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c > index a30e41a56085..9a1b006904a7 100644 > --- a/drivers/net/ppp/ppp_generic.c > +++ b/drivers/net/ppp/ppp_generic.c > @@ -1415,6 +1415,8 @@ static void __ppp_xmit_process(struct ppp *ppp, struct sk_buff *skb) > netif_wake_queue(ppp->dev); > else > netif_stop_queue(ppp->dev); > + } else { > + kfree_skb(skb); > } > ppp_xmit_unlock(ppp); > } nitpicking: i would suggest if (ppp->closing) kfree_skb(skb) else ...... i think that make that more easy to read as people tend to overlook things like *not*. re, wh