overflows while calculating volume->used_bytes

overflows while calculating volume->used_bytes

[Vinit Agnihotri]

I was experiencing overflows in multiplications for
volume->used_bytes in vmt.c & vtbl.c, while creating & resizing large volumes.

vol->used_bytes is long long however its 2 operands vol->used_ebs &
vol->usable_leb_size
are int. So their multiplication for larger values causes integer overflows.
Typecasting them solves the problem.

My machine & flash details:

64Bit dual-core AMD opteron, 1 GB RAM, linux 2.6.18.3.
mtd size = 6GB, volume size= 5GB, peb_size = 4MB.

heres patch which does the fix.

Signed-off-by: Vinit Agnihotri <vinit.agnihotri@gmail.com>
================================================================
diff -ruN linux-2.6.18.3-vanila/drivers/mtd/ubi/vmt.c
linux-2.6.18.3-mod/drivers/mtd/ubi/vmt.c
--- linux-2.6.18.3-vanila/drivers/mtd/ubi/vmt.c	2007-07-09
15:24:28.000000000 +0530
+++ linux-2.6.18.3-mod/drivers/mtd/ubi/vmt.c	2007-07-09 15:26:07.000000000 +0530
@@ -280,7 +280,8 @@
 	if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
 		vol->used_ebs = vol->reserved_pebs;
 		vol->last_eb_bytes = vol->usable_leb_size;
-		vol->used_bytes = vol->used_ebs * vol->usable_leb_size;
+		vol->used_bytes = (long long)vol->used_ebs *
+							(long long)vol->usable_leb_size;
 	} else {
 		bytes = vol->used_bytes;
 		vol->last_eb_bytes = do_div(bytes, vol->usable_leb_size);
@@ -538,7 +539,8 @@
 	if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
 		vol->used_ebs = reserved_pebs;
 		vol->last_eb_bytes = vol->usable_leb_size;
-		vol->used_bytes = vol->used_ebs * vol->usable_leb_size;
+		vol->used_bytes = (long long)vol->used_ebs *
+							(long long)vol->usable_leb_size;
 	}

 	paranoid_check_volumes(ubi);
@@ -739,7 +741,7 @@
 		goto fail;
 	}

-	n = vol->used_ebs * vol->usable_leb_size;
+	n = (long long)vol->used_ebs * (long long)vol->usable_leb_size;
 	if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
 		if (vol->corrupted != 0) {
 			ubi_err("corrupted dynamic volume");
diff -ruN linux-2.6.18.3-vanila/drivers/mtd/ubi/vtbl.c
linux-2.6.18.3-mod/drivers/mtd/ubi/vtbl.c
--- linux-2.6.18.3-vanila/drivers/mtd/ubi/vtbl.c	2007-07-09
15:26:52.000000000 +0530
+++ linux-2.6.18.3-mod/drivers/mtd/ubi/vtbl.c	2007-07-09
15:28:51.000000000 +0530
@@ -531,7 +531,8 @@
 		if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
 			vol->used_ebs = vol->reserved_pebs;
 			vol->last_eb_bytes = vol->usable_leb_size;
-			vol->used_bytes = vol->used_ebs * vol->usable_leb_size;
+			vol->used_bytes = (unsigned long)vol->used_ebs *
+								(unsigned long)vol->usable_leb_size;
 			continue;
 		}

@@ -561,7 +562,8 @@
 		}

 		vol->used_ebs = sv->used_ebs;
-		vol->used_bytes = (vol->used_ebs - 1) * vol->usable_leb_size;
+		vol->used_bytes = (unsigned long)(vol->used_ebs - 1) *
+							(unsigned long)vol->usable_leb_size;
 		vol->used_bytes += sv->last_data_size;
 		vol->last_eb_bytes = sv->last_data_size;
 	}
@@ -578,7 +580,8 @@
 	vol->usable_leb_size = ubi->leb_size;
 	vol->used_ebs = vol->reserved_pebs;
 	vol->last_eb_bytes = vol->reserved_pebs;
-	vol->used_bytes = vol->used_ebs * (ubi->leb_size - vol->data_pad);
+	vol->used_bytes = (unsigned long)vol->used_ebs *
+						(unsigned long)(ubi->leb_size - vol->data_pad);
 	vol->vol_id = UBI_LAYOUT_VOL_ID;

 	ubi_assert(!ubi->volumes[i]);

Thanks & Regards
Vinit.

Re: overflows while calculating volume->used_bytes

[Artem Bityutskiy]

Vinit,

On Tue, 2007-07-10 at 11:07 +0530, Vinit Agnihotri wrote:
> I was experiencing overflows in multiplications for
> volume->used_bytes in vmt.c & vtbl.c, while creating & resizing large volumes.
> 
> vol->used_bytes is long long however its 2 operands vol->used_ebs &
> vol->usable_leb_size
> are int. So their multiplication for larger values causes integer overflows.
> Typecasting them solves the problem.
> 
> My machine & flash details:
> 
> 64Bit dual-core AMD opteron, 1 GB RAM, linux 2.6.18.3.
> mtd size = 6GB, volume size= 5GB, peb_size = 4MB.
> 
> heres patch which does the fix.

Thanks for the patch. Just one note:

you can add only one (long long) prefix before the first operand, no
need to add it to the second one and make the line too long so that
you need to split it.

> +		vol->used_bytes = (long long)vol->used_ebs *
> +							(long long)vol->usable_leb_size;

Like here it could be
 +		vol->used_bytes = (long long)vol->used_ebs * vol->usable_leb_size;

Otherwise the patch looks good. Will you resend it or you are fine if I
amend it myself?

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

Re: overflows while calculating volume->used_bytes

[Vinit Agnihotri]

Heres the modified patch.
Not special purpose as such. Its just my flash is a bit large :)


Signed-off-by: Vinit Agnihotri <vinit.agnihotri@gmail.com>
================================================================
diff -ruN linux-2.6.18.3-vanila/drivers/mtd/ubi/vmt.c
linux-2.6.18.3-mod/drivers/mtd/ubi/vmt.c
--- linux-2.6.18.3-vanila/drivers/mtd/ubi/vmt.c	2007-07-09
15:24:28.000000000 +0530
+++ linux-2.6.18.3-mod/drivers/mtd/ubi/vmt.c	2007-07-10 13:25:41.000000000 +0530
@@ -280,7 +280,7 @@
 	if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
 		vol->used_ebs = vol->reserved_pebs;
 		vol->last_eb_bytes = vol->usable_leb_size;
-		vol->used_bytes = vol->used_ebs * vol->usable_leb_size;
+		vol->used_bytes = (long long)vol->used_ebs * vol->usable_leb_size;
 	} else {
 		bytes = vol->used_bytes;
 		vol->last_eb_bytes = do_div(bytes, vol->usable_leb_size);
@@ -538,7 +538,7 @@
 	if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
 		vol->used_ebs = reserved_pebs;
 		vol->last_eb_bytes = vol->usable_leb_size;
-		vol->used_bytes = vol->used_ebs * vol->usable_leb_size;
+		vol->used_bytes = (long long)vol->used_ebs * vol->usable_leb_size;
 	}

 	paranoid_check_volumes(ubi);
@@ -739,7 +739,7 @@
 		goto fail;
 	}

-	n = vol->used_ebs * vol->usable_leb_size;
+	n = (long long)vol->used_ebs * vol->usable_leb_size;
 	if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
 		if (vol->corrupted != 0) {
 			ubi_err("corrupted dynamic volume");
diff -ruN linux-2.6.18.3-vanila/drivers/mtd/ubi/vtbl.c
linux-2.6.18.3-mod/drivers/mtd/ubi/vtbl.c
--- linux-2.6.18.3-vanila/drivers/mtd/ubi/vtbl.c	2007-07-09
15:26:52.000000000 +0530
+++ linux-2.6.18.3-mod/drivers/mtd/ubi/vtbl.c	2007-07-10
13:27:18.000000000 +0530
@@ -531,7 +531,7 @@
 		if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
 			vol->used_ebs = vol->reserved_pebs;
 			vol->last_eb_bytes = vol->usable_leb_size;
-			vol->used_bytes = vol->used_ebs * vol->usable_leb_size;
+			vol->used_bytes = (unsigned long)vol->used_ebs * vol->usable_leb_size;
 			continue;
 		}

@@ -561,7 +561,8 @@
 		}

 		vol->used_ebs = sv->used_ebs;
-		vol->used_bytes = (vol->used_ebs - 1) * vol->usable_leb_size;
+		vol->used_bytes = (unsigned long)(vol->used_ebs - 1) *
+												vol->usable_leb_size;
 		vol->used_bytes += sv->last_data_size;
 		vol->last_eb_bytes = sv->last_data_size;
 	}
@@ -578,7 +579,8 @@
 	vol->usable_leb_size = ubi->leb_size;
 	vol->used_ebs = vol->reserved_pebs;
 	vol->last_eb_bytes = vol->reserved_pebs;
-	vol->used_bytes = vol->used_ebs * (ubi->leb_size - vol->data_pad);
+	vol->used_bytes = (unsigned long)vol->used_ebs *
+											(ubi->leb_size - vol->data_pad);
 	vol->vol_id = UBI_LAYOUT_VOL_ID;

 	ubi_assert(!ubi->volumes[i]);


On 7/10/07, Vinit Agnihotri <vinit.agnihotri@gmail.com> wrote:
> Yeah its true
> What I thought was having (long long) to both operands will make patch
> compiler independent.
>
> But yeah I modify patch & send u right away.
>
> On 7/10/07, Artem Bityutskiy <dedekind@infradead.org> wrote:
> > Vinit,
> >
> > On Tue, 2007-07-10 at 11:07 +0530, Vinit Agnihotri wrote:
> > > I was experiencing overflows in multiplications for
> > > volume->used_bytes in vmt.c & vtbl.c, while creating & resizing large volumes.
> > >
> > > vol->used_bytes is long long however its 2 operands vol->used_ebs &
> > > vol->usable_leb_size
> > > are int. So their multiplication for larger values causes integer overflows.
> > > Typecasting them solves the problem.
> > >
> > > My machine & flash details:
> > >
> > > 64Bit dual-core AMD opteron, 1 GB RAM, linux 2.6.18.3.
> > > mtd size = 6GB, volume size= 5GB, peb_size = 4MB.
> > >
> > > heres patch which does the fix.
> >
> > Thanks for the patch. Just one note:
> >
> > you can add only one (long long) prefix before the first operand, no
> > need to add it to the second one and make the line too long so that
> > you need to split it.
> >
> > > +             vol->used_bytes = (long long)vol->used_ebs *
> > > +                                                     (long long)vol->usable_leb_size;
> >
> > Like here it could be
> >  +              vol->used_bytes = (long long)vol->used_ebs * vol->usable_leb_size;
> >
> > Otherwise the patch looks good. Will you resend it or you are fine if I
> > amend it myself?
> >
> > --
> > Best regards,
> > Artem Bityutskiy (Битюцкий Артём)
> >
> >
>
>
> --
> I feel free now
>


-- 
I feel free now

Re: overflows while calculating volume->used_bytes

[Artem Bityutskiy]

On Tue, 2007-07-10 at 13:28 +0530, Vinit Agnihotri wrote:
> Heres the modified patch.
> Not special purpose as such. Its just my flash is a bit large :)

Committed the patch, thanks, although it did not apply cleanly and
I did hand work. Thy to save your mail and use git-am -i -s as I do.

P.S. It is so much easier to use git or quilt for preparing patches
then dealing with diff.

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)