* [PATCH] mtd: blktrans: fix integer overflow
@ 2015-08-21 14:57 Peng Fan
2015-09-02 17:02 ` Brian Norris
0 siblings, 1 reply; 4+ messages in thread
From: Peng Fan @ 2015-08-21 14:57 UTC (permalink / raw)
To: dwmw2, computersforpeace; +Cc: linux-mtd, linux-kernel, van.freenix
In drivers/mtd/mtd_blkdevs.c:
406 set_capacity(gd, (new->size * tr->blksize) >> 9);
The type of new->size is unsigned long and the type of tr->blksize is int,
the result of 'new->size * tr->blksize' may exceed ULONG_MAX on 32bit
machines.
I use nand chip MT29F32G08CBADBWP which is 4GB and the parameters passed
to kernel is 'mtdparts=gpmi-nand:-(user)', the whole nand chip will be
treated as a 4GB mtd partition. new->size is 0x800000 and tr->blksize is
0x200, 'new->size * tr->blksize' however is 0. This is what we do not want
to see.
Change the type of entry size of mtd_blktrans_dev to unsigned long long
to fix the overflow issue.
Signed-off-by: Peng Fan <van.freenix@gmail.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Brian Norris <computersforpeace@gmail.com>
---
include/linux/mtd/blktrans.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/mtd/blktrans.h b/include/linux/mtd/blktrans.h
index e93837f..3853d74 100644
--- a/include/linux/mtd/blktrans.h
+++ b/include/linux/mtd/blktrans.h
@@ -38,7 +38,7 @@ struct mtd_blktrans_dev {
struct mutex lock;
int devnum;
bool bg_stop;
- unsigned long size;
+ unsigned long long size;
int readonly;
int open;
struct kref ref;
--
1.8.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] mtd: blktrans: fix integer overflow
2015-08-21 14:57 [PATCH] mtd: blktrans: fix integer overflow Peng Fan
@ 2015-09-02 17:02 ` Brian Norris
2015-09-05 13:42 ` Peng Fan
0 siblings, 1 reply; 4+ messages in thread
From: Brian Norris @ 2015-09-02 17:02 UTC (permalink / raw)
To: Peng Fan; +Cc: dwmw2, linux-mtd, linux-kernel
On Fri, Aug 21, 2015 at 10:57:31PM +0800, Peng Fan wrote:
> In drivers/mtd/mtd_blkdevs.c:
> 406 set_capacity(gd, (new->size * tr->blksize) >> 9);
> The type of new->size is unsigned long and the type of tr->blksize is int,
> the result of 'new->size * tr->blksize' may exceed ULONG_MAX on 32bit
> machines.
>
> I use nand chip MT29F32G08CBADBWP which is 4GB and the parameters passed
> to kernel is 'mtdparts=gpmi-nand:-(user)', the whole nand chip will be
> treated as a 4GB mtd partition. new->size is 0x800000 and tr->blksize is
> 0x200, 'new->size * tr->blksize' however is 0. This is what we do not want
> to see.
>
> Change the type of entry size of mtd_blktrans_dev to unsigned long long
> to fix the overflow issue.
>
> Signed-off-by: Peng Fan <van.freenix@gmail.com>
> Cc: David Woodhouse <dwmw2@infradead.org>
> Cc: Brian Norris <computersforpeace@gmail.com>
> ---
> include/linux/mtd/blktrans.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/mtd/blktrans.h b/include/linux/mtd/blktrans.h
> index e93837f..3853d74 100644
> --- a/include/linux/mtd/blktrans.h
> +++ b/include/linux/mtd/blktrans.h
> @@ -38,7 +38,7 @@ struct mtd_blktrans_dev {
> struct mutex lock;
> int devnum;
> bool bg_stop;
> - unsigned long size;
> + unsigned long long size;
Sorry, you can't just do that. Some builds won't have right arithmetic
instructions (or compiler helpers) to do certain 64-bit operations, so you
either need to go and fix all the blktrans users to be more careful (e.g., do
bit shifts instead of division/modulo), or else find another solution. See, on
an ARM32 build:
LD init/built-in.o
drivers/built-in.o: In function `nftl_add_mtd':
:(.text+0x1369dc): undefined reference to `__aeabi_uldivmod'
:(.text+0x1369f4): undefined reference to `__aeabi_uldivmod'
:(.text+0x136a70): undefined reference to `__aeabi_uldivmod'
drivers/built-in.o: In function `inftl_add_mtd':
:(.text+0x137eb0): undefined reference to `__aeabi_uldivmod'
:(.text+0x137ec8): undefined reference to `__aeabi_uldivmod'
drivers/built-in.o::(.text+0x137f4c): more undefined references to `__aeabi_uldivmod' follow
> int readonly;
> int open;
> struct kref ref;
One possibility, since you only point to a single computation that
overflows, is to just fix the overflow locally. It's not like the 'size'
(which represents number of sectors) is actually ever overflowing a
32-bit integer. It's just the multiplication that overflows. So you
could cast to 64-bit arithmetic just for the multiplication. e.g.:
set_capcity(gd, ((u64)new->size * tr->blksize) >> 9);
Or some other creative solution.
Then, we don't have to address this problem till we start seeing 2TB
MTDs!
Brian
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] mtd: blktrans: fix integer overflow
2015-09-02 17:02 ` Brian Norris
@ 2015-09-05 13:42 ` Peng Fan
2015-09-09 23:37 ` Brian Norris
0 siblings, 1 reply; 4+ messages in thread
From: Peng Fan @ 2015-09-05 13:42 UTC (permalink / raw)
To: Brian Norris; +Cc: dwmw2, linux-mtd, linux-kernel
On Wed, Sep 02, 2015 at 10:02:49AM -0700, Brian Norris wrote:
> On Fri, Aug 21, 2015 at 10:57:31PM +0800, Peng Fan wrote:
> > In drivers/mtd/mtd_blkdevs.c:
> > 406 set_capacity(gd, (new->size * tr->blksize) >> 9);
> > The type of new->size is unsigned long and the type of tr->blksize is int,
> > the result of 'new->size * tr->blksize' may exceed ULONG_MAX on 32bit
> > machines.
> >
> > I use nand chip MT29F32G08CBADBWP which is 4GB and the parameters passed
> > to kernel is 'mtdparts=gpmi-nand:-(user)', the whole nand chip will be
> > treated as a 4GB mtd partition. new->size is 0x800000 and tr->blksize is
> > 0x200, 'new->size * tr->blksize' however is 0. This is what we do not want
> > to see.
> >
> > Change the type of entry size of mtd_blktrans_dev to unsigned long long
> > to fix the overflow issue.
> >
> > Signed-off-by: Peng Fan <van.freenix@gmail.com>
> > Cc: David Woodhouse <dwmw2@infradead.org>
> > Cc: Brian Norris <computersforpeace@gmail.com>
> > ---
> > include/linux/mtd/blktrans.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/mtd/blktrans.h b/include/linux/mtd/blktrans.h
> > index e93837f..3853d74 100644
> > --- a/include/linux/mtd/blktrans.h
> > +++ b/include/linux/mtd/blktrans.h
> > @@ -38,7 +38,7 @@ struct mtd_blktrans_dev {
> > struct mutex lock;
> > int devnum;
> > bool bg_stop;
> > - unsigned long size;
> > + unsigned long long size;
>
> Sorry, you can't just do that. Some builds won't have right arithmetic
> instructions (or compiler helpers) to do certain 64-bit operations, so you
> either need to go and fix all the blktrans users to be more careful (e.g., do
> bit shifts instead of division/modulo), or else find another solution. See, on
> an ARM32 build:
>
> LD init/built-in.o
> drivers/built-in.o: In function `nftl_add_mtd':
> :(.text+0x1369dc): undefined reference to `__aeabi_uldivmod'
> :(.text+0x1369f4): undefined reference to `__aeabi_uldivmod'
> :(.text+0x136a70): undefined reference to `__aeabi_uldivmod'
> drivers/built-in.o: In function `inftl_add_mtd':
> :(.text+0x137eb0): undefined reference to `__aeabi_uldivmod'
> :(.text+0x137ec8): undefined reference to `__aeabi_uldivmod'
> drivers/built-in.o::(.text+0x137f4c): more undefined references to `__aeabi_uldivmod' follow
>
My bad. I only tested this patch on i.mx6 platform, but not take other platforms into consideration.
> > int readonly;
> > int open;
> > struct kref ref;
>
> One possibility, since you only point to a single computation that
> overflows, is to just fix the overflow locally. It's not like the 'size'
> (which represents number of sectors) is actually ever overflowing a
> 32-bit integer. It's just the multiplication that overflows. So you
> could cast to 64-bit arithmetic just for the multiplication. e.g.:
>
> set_capcity(gd, ((u64)new->size * tr->blksize) >> 9);
Yeah. It is the multiplication overflowing a 32-bit interger. My frist implementation is this way, using u64 to do type cast.
But I guess one day the number of sectors can be larger than UINT_MAX, so I change it to 'unsigned long long' from 'unsigned long', which is
not the right way, thanks for correcting me.
>
> Or some other creative solution.
I think this should be a bug fix. If you need a quick fix, I can send out the simple patch that just do (u64) cast. If not, I can take
some time to "fix all the blktrans users".
Regards,
Peng.
>
> Then, we don't have to address this problem till we start seeing 2TB
> MTDs!
>
> Brian
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] mtd: blktrans: fix integer overflow
2015-09-05 13:42 ` Peng Fan
@ 2015-09-09 23:37 ` Brian Norris
0 siblings, 0 replies; 4+ messages in thread
From: Brian Norris @ 2015-09-09 23:37 UTC (permalink / raw)
To: Peng Fan; +Cc: dwmw2, linux-mtd, linux-kernel
On Sat, Sep 05, 2015 at 09:42:27PM +0800, Peng Fan wrote:
> On Wed, Sep 02, 2015 at 10:02:49AM -0700, Brian Norris wrote:
> > One possibility, since you only point to a single computation that
> > overflows, is to just fix the overflow locally. It's not like the 'size'
> > (which represents number of sectors) is actually ever overflowing a
> > 32-bit integer. It's just the multiplication that overflows. So you
> > could cast to 64-bit arithmetic just for the multiplication. e.g.:
> >
> > set_capcity(gd, ((u64)new->size * tr->blksize) >> 9);
>
> Yeah. It is the multiplication overflowing a 32-bit interger. My frist
> implementation is this way, using u64 to do type cast. But I guess one
> day the number of sectors can be larger than UINT_MAX, so I change it
> to 'unsigned long long' from 'unsigned long', which is
> not the right way, thanks for correcting me.
> >
> > Or some other creative solution.
>
> I think this should be a bug fix. If you need a quick fix, I can send
> out the simple patch that just do (u64) cast. If not, I can take some
> time to "fix all the blktrans users".
I think since you've identified (and tested) a fix, we might as well
include it. So I suppose the cast approach. The larger change would be
more invasive and may take a while.
> >
> > Then, we don't have to address this problem till we start seeing 2TB
> > MTDs!
Brian
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2015-09-09 23:37 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-08-21 14:57 [PATCH] mtd: blktrans: fix integer overflow Peng Fan
2015-09-02 17:02 ` Brian Norris
2015-09-05 13:42 ` Peng Fan
2015-09-09 23:37 ` Brian Norris
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).