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Date: Wed, 16 Jul 2008 19:12:01 +0300
From: "Nick Kossifidis" <mickflemm@...il.com>
To: "Jiri Slaby" <jirislaby@...il.com>
Cc: linville@...driver.com, linux-wireless@...r.kernel.org,
linux-kernel@...r.kernel.org,
"Luis R. Rodriguez" <mcgrof@...il.com>
Subject: Re: [PATCH 1/5] Ath5k: fix memory corruption
2008/7/15 Jiri Slaby <jirislaby@...il.com>:
> When signal is noisy, hardware can use all RX buffers and since the last
> entry in the list is self-linked, it overwrites the entry until we link
> new buffers.
>
> Ensure that we don't free this last one until we are 100% sure that it
> is not used by the hardware anymore to not cause memory curruption as
> can be seen below.
>
> This is done by checking next buffer in the list. Even after that we
> know that the hardware refetched the new link and proceeded further
> (the next buffer is ready) we can finally free the overwritten buffer.
>
> We discard it since the status in its descriptor is overwritten (OR-ed
> by new status) too.
>
> =============================================================================
> BUG kmalloc-4096: Poison overwritten
> -----------------------------------------------------------------------------
>
> INFO: 0xffff810067419060-0xffff810067419667. First byte 0x8 instead of 0x6b
> INFO: Allocated in dev_alloc_skb+0x18/0x30 age=1118 cpu=1 pid=0
> INFO: Freed in skb_release_data+0x85/0xd0 age=1105 cpu=1 pid=3718
> INFO: Slab 0xffffe200019d0600 objects=7 used=0 fp=0xffff810067419048 flags=0x40000000000020c3
> INFO: Object 0xffff810067419048 @offset=4168 fp=0xffff81006741c120
>
> Bytes b4 0xffff810067419038: 4f 0b 02 00 01 00 00 00 5a 5a 5a 5a 5a 5a 5a 5a O.......ZZZZZZZZ
> Object 0xffff810067419048: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
> Object 0xffff810067419058: 6b 6b 6b 6b 6b 6b 6b 6b 08 42 30 00 00 0b 6b 80 kkkkkkkk.B0...k.
> Object 0xffff810067419068: f0 5d 00 4f 62 08 a3 64 00 0c 42 16 52 e4 f0 5a 360].Ob.243d..B.R344360Z
> Object 0xffff810067419078: 68 81 00 00 7b a5 b4 be 7d 3b 8f 53 cd d5 de 12 h...{245264276};.S315325336.
> Object 0xffff810067419088: 96 10 0b 89 48 54 23 41 0f 4e 2d b9 37 c3 cb 29 ....HT#A.N-2717303313)
> Object 0xffff810067419098: d1 e0 de 14 8a 57 2a cc 3b 44 0d 78 7a 19 12 15 321340336..W*314;D.xz...
> Object 0xffff8100674190a8: a9 ec d4 35 a8 10 ec 8c 40 a7 06 0a 51 a7 48 bb 2513543245250.354.@.....Q247H273
> Object 0xffff8100674190b8: 3e cf a1 c7 38 60 63 3f 51 15 c7 20 eb ba 65 30 >ϡ3078`c?Q.307.353272e0
> Redzone 0xffff81006741a048: bb bb bb bb bb bb bb bb 273273273273273273273273
> Padding 0xffff81006741a088: 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ
> Pid: 3297, comm: ath5k_pci Not tainted 2.6.26-rc8-mm1_64 #427
>
> Call Trace:
> [<ffffffff802a7306>] print_trailer+0xf6/0x150
> [<ffffffff802a7485>] check_bytes_and_report+0x125/0x180
> [<ffffffff802a75dc>] check_object+0xac/0x260
> [<ffffffff802a9308>] __slab_alloc+0x368/0x6d0
> [<ffffffff80544f82>] ? wireless_send_event+0x142/0x310
> [<ffffffff804b1bd4>] ? __alloc_skb+0x44/0x150
> [<ffffffff80544f82>] ? wireless_send_event+0x142/0x310
> [<ffffffff802aa853>] __kmalloc_track_caller+0xc3/0xf0
> [<ffffffff804b1bfe>] __alloc_skb+0x6e/0x150
> [... stack snipped]
>
> FIX kmalloc-4096: Restoring 0xffff810067419060-0xffff810067419667=0x6b
>
> FIX kmalloc-4096: Marking all objects used
>
> Signed-off-by: Jiri Slaby <jirislaby@...il.com>
> Cc: Nick Kossifidis <mickflemm@...il.com>
> Cc: Luis R. Rodriguez <mcgrof@...il.com>
> ---
> drivers/net/wireless/ath5k/base.c | 32 +++++++++++++++++++++++++-------
> drivers/net/wireless/ath5k/base.h | 2 +-
> 2 files changed, 26 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/net/wireless/ath5k/base.c b/drivers/net/wireless/ath5k/base.c
> index 12a9443..e9ec284 100644
> --- a/drivers/net/wireless/ath5k/base.c
> +++ b/drivers/net/wireless/ath5k/base.c
> @@ -1683,20 +1683,21 @@ ath5k_tasklet_rx(unsigned long data)
> struct ath5k_rx_status rs = {};
> struct sk_buff *skb;
> struct ath5k_softc *sc = (void *)data;
> - struct ath5k_buf *bf;
> + struct ath5k_buf *bf, *bf_last;
> struct ath5k_desc *ds;
> int ret;
> int hdrlen;
> int pad;
>
> spin_lock(&sc->rxbuflock);
> + if (list_empty(&sc->rxbuf)) {
> + ATH5K_WARN(sc, "empty rx buf pool\n");
> + goto unlock;
> + }
> + bf_last = list_entry(sc->rxbuf.prev, struct ath5k_buf, list);
> do {
> rxs.flag = 0;
>
> - if (unlikely(list_empty(&sc->rxbuf))) {
> - ATH5K_WARN(sc, "empty rx buf pool\n");
> - break;
> - }
> bf = list_first_entry(&sc->rxbuf, struct ath5k_buf, list);
> BUG_ON(bf->skb == NULL);
> skb = bf->skb;
> @@ -1706,8 +1707,24 @@ ath5k_tasklet_rx(unsigned long data)
> pci_dma_sync_single_for_cpu(sc->pdev, sc->desc_daddr,
> sc->desc_len, PCI_DMA_FROMDEVICE);
>
> - if (unlikely(ds->ds_link == bf->daddr)) /* this is the end */
> - break;
> + /*
> + * last buffer must not be freed to ensure proper hardware
> + * function. When the hardware finishes also a packet next to
> + * it, we are sure, it doesn't use it anymore and we can go on.
> + */
> + if (bf_last == bf)
> + bf->flags |= 1;
> + if (bf->flags) {
> + struct ath5k_buf *bf_next = list_entry(bf->list.next,
> + struct ath5k_buf, list);
> + ret = sc->ah->ah_proc_rx_desc(sc->ah, bf_next->desc,
> + &rs);
> + if (ret)
> + break;
> + bf->flags &= ~1;
> + /* skip the overwritten one (even status is martian) */
> + goto next;
> + }
>
> ret = sc->ah->ah_proc_rx_desc(sc->ah, ds, &rs);
> if (unlikely(ret == -EINPROGRESS))
> @@ -1817,6 +1834,7 @@ accept:
> next:
> list_move_tail(&bf->list, &sc->rxbuf);
> } while (ath5k_rxbuf_setup(sc, bf) == 0);
> +unlock:
> spin_unlock(&sc->rxbuflock);
> }
>
> diff --git a/drivers/net/wireless/ath5k/base.h b/drivers/net/wireless/ath5k/base.h
> index 47f414b..d7e03e6 100644
> --- a/drivers/net/wireless/ath5k/base.h
> +++ b/drivers/net/wireless/ath5k/base.h
> @@ -56,7 +56,7 @@
>
> struct ath5k_buf {
> struct list_head list;
> - unsigned int flags; /* tx descriptor flags */
> + unsigned int flags; /* rx descriptor flags */
> struct ath5k_desc *desc; /* virtual addr of desc */
> dma_addr_t daddr; /* physical addr of desc */
> struct sk_buff *skb; /* skbuff for buf */
> --
> 1.5.6.2
>
>
Nice catch ;-)
Acked-by: Nick Kossifidis <mickflemm@...il.com>
--
GPG ID: 0xD21DB2DB
As you read this post global entropy rises. Have Fun ;-)
Nick
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