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ppp: Fix memory leak in ppp_write

PATCH In review Takeshi Misawa 3 participants 3 messages Sep 14, 2019 – Sep 17, 2019

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Takeshi Misawa

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#0 lore raw

PATCH 1/1 ppp: Fix memory leak in ppp_write

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 [email protected]
Signed-off-by Takeshi Misawa <[email protected]>

---
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(+)
drivers/net/ppp/ppp_generic.c +2 -0
index a30e41a56085..9a1b006904a7 100644
@@ -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);
 }
Signature · 1 line
2.17.1
#1 lore raw

Am 14.09.2019 06:09, schrieb Takeshi Misawa:

Quoted 51 lines

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 [email protected]
Signed-off-by Takeshi Misawa <[email protected]>

---
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(+)
drivers/net/ppp/ppp_generic.c +0 -0
index a30e41a56085..9a1b006904a7 100644

drivers/net/ppp/ppp_generic.c static void __ppp_xmit_process(struct ppp *ppp, struct sk_buff *skb) · line 1422

Quoted 8 lines
drivers/net/ppp/ppp_generic.c +2 -0
@@ -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

#2 lore raw
In reply to Takeshi Misawa
Quoted 32 lines · 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 [email protected]
Signed-off-by Takeshi Misawa <[email protected]>
Quoted 9 lines

---
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.

Hi Takeshi,

Kernel networking patches are reviewed on netdev ML. Your patch looks good but the description misses a Fixes tag:

Fixes 6d066734e9f0 ("ppp: avoid loop in xmit recursion detection code")

Can you please send this patch formally to netdev? Don't forget to indicate which tree you're tagetting in the subject. In this case, it should be [PATCH net] (see Documentation/networking/netdev-FAQ.rst for details).

Thanks for fixing my bug :)

Guillaume