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From: Darren Kenny <darren.kenny@oracle.com>
To: P J P <ppandit@redhat.com>, QEMU Developers <qemu-devel@nongnu.org>
Cc: "Fam Zheng" <fam@euphon.net>,
	"Prasad J Pandit" <pjp@fedoraproject.org>,
	"Alexander Bulekov" <alxndr@bu.edu>,
	"Marc-André Lureau" <marcandre.lureau@redhat.com>,
	"Ding Ren" <rding@gatech.edu>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Philippe Mathieu-Daudé" <philmd@redhat.com>,
	"Hanqing Zhao" <hanqing@gatech.edu>
Subject: Re: [PATCH v2 1/3] megasas: use unsigned type for reply_queue_head and check index
Date: Thu, 14 May 2020 14:19:08 +0100	[thread overview]
Message-ID: <m2k11ek62b.fsf@oracle.com> (raw)
In-Reply-To: <20200513192540.1583887-2-ppandit@redhat.com>

Hi Prasad,

On Thursday, 2020-05-14 at 00:55:38 +0530, P J P wrote:
> From: Prasad J Pandit <pjp@fedoraproject.org>
>
> A guest user may set 'reply_queue_head' field of MegasasState to
> a negative value. Later in 'megasas_lookup_frame' it is used to
> index into s->frames[] array. Use unsigned type to avoid OOB
> access issue.
>
> Also check that 'index' value stays within s->frames[] bounds
> through the while() loop in 'megasas_lookup_frame' to avoid OOB
> access.
>
> Reported-by: Ren Ding <rding@gatech.edu>
> Reported-by: Hanqing Zhao <hanqing@gatech.edu>
> Reported-by: Alexander Bulekov <alxndr@bu.edu>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
>  hw/scsi/megasas.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> Update v1 -> v2: fix OOB access when index > MEGASAS_MAX_FRAMES(=2048)
>  -> https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg03131.html
>
> diff --git a/hw/scsi/megasas.c b/hw/scsi/megasas.c
> index af18c88b65..6ce598cd69 100644
> --- a/hw/scsi/megasas.c
> +++ b/hw/scsi/megasas.c
> @@ -112,7 +112,7 @@ typedef struct MegasasState {
>      uint64_t reply_queue_pa;
>      void *reply_queue;
>      int reply_queue_len;
> -    int reply_queue_head;
> +    uint16_t reply_queue_head;
>      int reply_queue_tail;
>      uint64_t consumer_pa;
>      uint64_t producer_pa;
> @@ -445,7 +445,7 @@ static MegasasCmd *megasas_lookup_frame(MegasasState *s,
>  
>      index = s->reply_queue_head;

While it is probably unlikely that it would cause an integer underflow
here, for consistency, index probably should also be declared as
unsigned, but from what I can tell it is still an 'int'.

Thanks,

Darren.

>  
> -    while (num < s->fw_cmds) {
> +    while (num < s->fw_cmds && index < MEGASAS_MAX_FRAMES) {
>          if (s->frames[index].pa && s->frames[index].pa == frame) {
>              cmd = &s->frames[index];
>              break;
> -- 
> 2.25.4


  parent reply	other threads:[~2020-05-14 13:20 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-13 19:25 [PATCH v2 0/3] Megasas: fix OOB access and NULL dereference issues P J P
2020-05-13 19:25 ` [PATCH v2 1/3] megasas: use unsigned type for reply_queue_head and check index P J P
2020-05-13 20:31   ` Alexander Bulekov
2020-05-14 13:19   ` Darren Kenny [this message]
2020-05-14 16:10     ` P J P
2020-05-13 19:25 ` [PATCH v2 2/3] megasas: avoid NULL pointer dereference P J P
2020-05-13 20:20   ` Alexander Bulekov
2020-05-14 13:19   ` Darren Kenny
2020-05-21 15:34   ` Paolo Bonzini
2020-05-26  7:18     ` P J P
2020-05-26  7:49       ` Paolo Bonzini
2020-05-13 19:25 ` [PATCH v2 3/3] megasas: use unsigned type for positive numeric fields P J P
2020-05-14 13:28   ` Darren Kenny
2020-05-21 15:35 ` [PATCH v2 0/3] Megasas: fix OOB access and NULL dereference issues Paolo Bonzini

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