Re: [PATCH v1 3/3] crypto: ccp - Protect against poorly marked end of sg list
On 05/27/2015 07:36 PM, Herbert Xu wrote: On Wed, May 27, 2015 at 09:12:02AM -0500, Tom Lendacky wrote: The reason I'm asking is because while this patch fixes your driver everybody else will still crash and burn should something like this happen again. A number of other drivers already have similar sg-count functions in them. Perhaps you can help abstract this into a helper that everybody can call? I can do that. Something like an sg_nents_for_len() function that takes an sg pointer and a u64 length as arguments. The function should also return an error if the length requirement isn't satisfied. Thanks, Tom Cheers, -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v1 3/3] crypto: ccp - Protect against poorly marked end of sg list
On Wed, May 27, 2015 at 09:12:02AM -0500, Tom Lendacky wrote: > > >The reason I'm asking is because while this patch fixes your driver > >everybody else will still crash and burn should something like this > >happen again. > > A number of other drivers already have similar sg-count functions in > them. Perhaps you can help abstract this into a helper that everybody can call? Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v1 3/3] crypto: ccp - Protect against poorly marked end of sg list
On 05/27/2015 04:45 AM, Herbert Xu wrote:
On Wed, May 27, 2015 at 05:43:05PM +0800, Herbert Xu wrote:
Tom Lendacky wrote:
Scatter gather lists can be created with more available entries than are
actually used (e.g. using sg_init_table() to reserve a specific number
of sg entries, but in actuality using something less than that based on
the data length). The caller sometimes fails to mark the last entry
with sg_mark_end(). In these cases, sg_nents() will return the original
size of the sg list as opposed to the actual number of sg entries that
contain valid data.
On arm64, if the sg_nents() value is used in a call to dma_map_sg() in
this situation, then it causes a BUG_ON in lib/swiotlb.c because an
"empty" sg list entry results in dma_capable() returning false and
swiotlb trying to create a bounce buffer of size 0. This occurred in
the userspace crypto interface before being fixed by
0f477b655a52 ("crypto: algif - Mark sgl end at the end of data")
Protect against this in the future by counting the number of sg entries
needed to meet the length requirement and supplying that value to
dma_map_sg().
Is this needed for any reason other than this bug that's already
been fixed?
Could this be needed if you have a properly marked SG list say of
100 bytes but len is only 10 bytes?
I don't think that situation matters because the DMA mapping should
succeed just fine at 100 bytes even if only needing/using 10 bytes.
Thanks,
Tom
Cheers,
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Re: [PATCH v1 3/3] crypto: ccp - Protect against poorly marked end of sg list
On 05/27/2015 04:43 AM, Herbert Xu wrote:
Tom Lendacky wrote:
Scatter gather lists can be created with more available entries than are
actually used (e.g. using sg_init_table() to reserve a specific number
of sg entries, but in actuality using something less than that based on
the data length). The caller sometimes fails to mark the last entry
with sg_mark_end(). In these cases, sg_nents() will return the original
size of the sg list as opposed to the actual number of sg entries that
contain valid data.
On arm64, if the sg_nents() value is used in a call to dma_map_sg() in
this situation, then it causes a BUG_ON in lib/swiotlb.c because an
"empty" sg list entry results in dma_capable() returning false and
swiotlb trying to create a bounce buffer of size 0. This occurred in
the userspace crypto interface before being fixed by
0f477b655a52 ("crypto: algif - Mark sgl end at the end of data")
Protect against this in the future by counting the number of sg entries
needed to meet the length requirement and supplying that value to
dma_map_sg().
Is this needed for any reason other than this bug that's already
been fixed?
I added this just to protect against any other users of the API that
may do something similar in the future (or if the user should re-use
an sg list and leave leftover sg entries in it). Since software
crypto implementations walk the sg list based on length and do not use
DMA mappings it is possible for this bug to pop up again in another
location since it is likely that the testing won't be done with
hardware crypto devices.
The reason I'm asking is because while this patch fixes your driver
everybody else will still crash and burn should something like this
happen again.
A number of other drivers already have similar sg-count functions in
them.
I'm ok if you decide that this patch shouldn't be applied. It's just
that this is typically an issue that won't be found until after the
release of a kernel rather than during the development stages.
Thanks,
Tom
Cheers,
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Re: [PATCH v1 3/3] crypto: ccp - Protect against poorly marked end of sg list
On Wed, May 27, 2015 at 05:43:05PM +0800, Herbert Xu wrote:
> Tom Lendacky wrote:
> > Scatter gather lists can be created with more available entries than are
> > actually used (e.g. using sg_init_table() to reserve a specific number
> > of sg entries, but in actuality using something less than that based on
> > the data length). The caller sometimes fails to mark the last entry
> > with sg_mark_end(). In these cases, sg_nents() will return the original
> > size of the sg list as opposed to the actual number of sg entries that
> > contain valid data.
> >
> > On arm64, if the sg_nents() value is used in a call to dma_map_sg() in
> > this situation, then it causes a BUG_ON in lib/swiotlb.c because an
> > "empty" sg list entry results in dma_capable() returning false and
> > swiotlb trying to create a bounce buffer of size 0. This occurred in
> > the userspace crypto interface before being fixed by
> >
> > 0f477b655a52 ("crypto: algif - Mark sgl end at the end of data")
> >
> > Protect against this in the future by counting the number of sg entries
> > needed to meet the length requirement and supplying that value to
> > dma_map_sg().
>
> Is this needed for any reason other than this bug that's already
> been fixed?
Could this be needed if you have a properly marked SG list say of
100 bytes but len is only 10 bytes?
Cheers,
--
Email: Herbert Xu
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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Re: [PATCH v1 3/3] crypto: ccp - Protect against poorly marked end of sg list
Tom Lendacky wrote:
> Scatter gather lists can be created with more available entries than are
> actually used (e.g. using sg_init_table() to reserve a specific number
> of sg entries, but in actuality using something less than that based on
> the data length). The caller sometimes fails to mark the last entry
> with sg_mark_end(). In these cases, sg_nents() will return the original
> size of the sg list as opposed to the actual number of sg entries that
> contain valid data.
>
> On arm64, if the sg_nents() value is used in a call to dma_map_sg() in
> this situation, then it causes a BUG_ON in lib/swiotlb.c because an
> "empty" sg list entry results in dma_capable() returning false and
> swiotlb trying to create a bounce buffer of size 0. This occurred in
> the userspace crypto interface before being fixed by
>
> 0f477b655a52 ("crypto: algif - Mark sgl end at the end of data")
>
> Protect against this in the future by counting the number of sg entries
> needed to meet the length requirement and supplying that value to
> dma_map_sg().
Is this needed for any reason other than this bug that's already
been fixed?
The reason I'm asking is because while this patch fixes your driver
everybody else will still crash and burn should something like this
happen again.
Cheers,
--
Email: Herbert Xu
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
--
To unsubscribe from this list: send the line "unsubscribe linux-crypto" in
the body of a message to majord...@vger.kernel.org
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[PATCH v1 3/3] crypto: ccp - Protect against poorly marked end of sg list
Scatter gather lists can be created with more available entries than are
actually used (e.g. using sg_init_table() to reserve a specific number
of sg entries, but in actuality using something less than that based on
the data length). The caller sometimes fails to mark the last entry
with sg_mark_end(). In these cases, sg_nents() will return the original
size of the sg list as opposed to the actual number of sg entries that
contain valid data.
On arm64, if the sg_nents() value is used in a call to dma_map_sg() in
this situation, then it causes a BUG_ON in lib/swiotlb.c because an
"empty" sg list entry results in dma_capable() returning false and
swiotlb trying to create a bounce buffer of size 0. This occurred in
the userspace crypto interface before being fixed by
0f477b655a52 ("crypto: algif - Mark sgl end at the end of data")
Protect against this in the future by counting the number of sg entries
needed to meet the length requirement and supplying that value to
dma_map_sg().
Signed-off-by: Tom Lendacky
---
drivers/crypto/ccp/ccp-ops.c | 18 +-
1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/drivers/crypto/ccp/ccp-ops.c b/drivers/crypto/ccp/ccp-ops.c
index 542453c..8377ed6 100644
--- a/drivers/crypto/ccp/ccp-ops.c
+++ b/drivers/crypto/ccp/ccp-ops.c
@@ -477,6 +477,22 @@ static u32 ccp_gen_jobid(struct ccp_device *ccp)
return atomic_inc_return(&ccp->current_id) & CCP_JOBID_MASK;
}
+static int ccp_sg_nents(struct scatterlist *sg, u64 len)
+{
+ int nents = 0;
+
+ while (sg && len) {
+ nents++;
+ if (sg->length > len)
+ break;
+
+ len -= sg->length;
+ sg = sg_next(sg);
+ }
+
+ return nents;
+}
+
static void ccp_sg_free(struct ccp_sg_workarea *wa)
{
if (wa->dma_count)
@@ -495,7 +511,7 @@ static int ccp_init_sg_workarea(struct ccp_sg_workarea *wa,
struct device *dev,
if (!sg)
return 0;
- wa->nents = sg_nents(sg);
+ wa->nents = ccp_sg_nents(sg, len);
wa->bytes_left = len;
wa->sg_used = 0;
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