diff mbox series

[v2] slof/fs/packages/disk-label.fs: improve checking for DOS boot partitions

Message ID 20240318103003.484602-1-kconsul@linux.vnet.ibm.com
State Superseded
Headers show
Series [v2] slof/fs/packages/disk-label.fs: improve checking for DOS boot partitions | expand

Commit Message

Kautuk Consul March 18, 2024, 10:30 a.m. UTC
While testing with a qcow2 with a DOS boot partition it was found that
when we set the logical_block_size in the guest XML to >512 then the
boot would fail in the following interminable loop:
<SNIP>
Trying to load:  from: /pci@800000020000000/scsi@3 ... virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
</SNIP>

Change the count-dos-logical-partitions Forth subroutine and the Forth
subroutines calling count-dos-logical-partitions to check for this access
beyond end of device error.

After making the above changes, it fails properly with the correct error
message as follows:
<SNIP>
Trying to load:  from: /pci@800000020000000/scsi@3 ... virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!
virtioblk_transfer: Access beyond end of device!

E3404: Not a bootable device!

E3407: Load failed

  Type 'boot' and press return to continue booting the system.
  Type 'reset-all' and press return to reboot the system.

Ready!
0 >
</SNIP>

Signed-off-by: Kautuk Consul <kconsul@linux.vnet.ibm.com>
---
 slof/fs/packages/disk-label.fs | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

Comments

Thomas Huth March 26, 2024, 2:45 p.m. UTC | #1
On 18/03/2024 11.30, Kautuk Consul wrote:
> While testing with a qcow2 with a DOS boot partition it was found that
> when we set the logical_block_size in the guest XML to >512 then the
> boot would fail 
...
> diff --git a/slof/fs/packages/disk-label.fs b/slof/fs/packages/disk-label.fs
> index 661c6b0..2630701 100644
> --- a/slof/fs/packages/disk-label.fs
> +++ b/slof/fs/packages/disk-label.fs
> @@ -132,11 +132,16 @@ CONSTANT /gpt-part-entry
>      debug-disk-label? IF dup ." actual=" .d cr THEN
>   ;
>   
> -\ read sector to array "block"
> -: read-sector ( sector-number -- )
> +\ read sector to array "block" and return actual bytes read
> +: read-sector-ret ( sector-number -- actual-bytes )
>      \ block-size is 0x200 on disks, 0x800 on cdrom drives
>      block-size * 0 seek drop      \ seek to sector
> -   block block-size read drop    \ read sector
> +   block block-size read    \ read sector
> +;
> +
> +\ read sector to array "block"
> +: read-sector ( sector-number -- )
> +   read-sector-ret drop
>   ;
>   
>   : (.part-entry) ( part-entry )
> @@ -204,7 +209,8 @@ CONSTANT /gpt-part-entry
>            part-entry>sector-offset l@-le    ( current sector )
>            dup to part-start to lpart-start  ( current )

I just noticed that according to the stack comment above, there is a 
"current" item on the stack...

>            BEGIN
> -            part-start read-sector          \ read EBR
> +            part-start read-sector-ret          \ read EBR
> +            block-size < IF UNLOOP 0 EXIT THEN

... which doesn't get dropped here before the EXIT ? Is the stack still 
right after this function exited early?

>               1 partition>start-sector IF
>                  \ ." Logical Partition found at " part-start .d cr
>                  1+
> @@ -279,6 +285,7 @@ CONSTANT /gpt-part-entry
>      THEN
>   
>      count-dos-logical-partitions TO dos-logical-partitions
> +   dos-logical-partitions 0= IF false EXIT THEN
>   
>      debug-disk-label? IF
>         ." Found " dos-logical-partitions .d ." logical partitions" cr
> @@ -352,6 +359,7 @@ CONSTANT /gpt-part-entry
>      no-mbr? IF drop FALSE EXIT THEN  \ read MBR and check for DOS disk-label magic
>   
>      count-dos-logical-partitions TO dos-logical-partitions
> +   dos-logical-partitions 0= IF 0 EXIT THEN

Similar question here, what about the "addr" stack item? Shouldn't it be 
dropped first?

  Thomas


PS: I'm still having trouble receiving your mail, I just discovered v2 on 
patchwork and downloaded it from there...
Kautuk Consul March 26, 2024, 3:30 p.m. UTC | #2
Hi,

On 2024-03-26 15:45:46, Thomas Huth wrote:
> On 18/03/2024 11.30, Kautuk Consul wrote:
> > While testing with a qcow2 with a DOS boot partition it was found that
> > when we set the logical_block_size in the guest XML to >512 then the
> > boot would fail
> ...
> > diff --git a/slof/fs/packages/disk-label.fs b/slof/fs/packages/disk-label.fs
> > index 661c6b0..2630701 100644
> > --- a/slof/fs/packages/disk-label.fs
> > +++ b/slof/fs/packages/disk-label.fs
> > @@ -132,11 +132,16 @@ CONSTANT /gpt-part-entry
> >      debug-disk-label? IF dup ." actual=" .d cr THEN
> >   ;
> > -\ read sector to array "block"
> > -: read-sector ( sector-number -- )
> > +\ read sector to array "block" and return actual bytes read
> > +: read-sector-ret ( sector-number -- actual-bytes )
> >      \ block-size is 0x200 on disks, 0x800 on cdrom drives
> >      block-size * 0 seek drop      \ seek to sector
> > -   block block-size read drop    \ read sector
> > +   block block-size read    \ read sector
> > +;
> > +
> > +\ read sector to array "block"
> > +: read-sector ( sector-number -- )
> > +   read-sector-ret drop
> >   ;
> >   : (.part-entry) ( part-entry )
> > @@ -204,7 +209,8 @@ CONSTANT /gpt-part-entry
> >            part-entry>sector-offset l@-le    ( current sector )
> >            dup to part-start to lpart-start  ( current )
> 
> I just noticed that according to the stack comment above, there is a
> "current" item on the stack...
> 
> >            BEGIN
> > -            part-start read-sector          \ read EBR
> > +            part-start read-sector-ret          \ read EBR
> > +            block-size < IF UNLOOP 0 EXIT THEN
> 
> ... which doesn't get dropped here before the EXIT ? Is the stack still
> right after this function exited early?

Thanks for catching this. I didn't notice this as I sent this v2 in a
hurry.

> 
> >               1 partition>start-sector IF
> >                  \ ." Logical Partition found at " part-start .d cr
> >                  1+
> > @@ -279,6 +285,7 @@ CONSTANT /gpt-part-entry
> >      THEN
> >      count-dos-logical-partitions TO dos-logical-partitions
> > +   dos-logical-partitions 0= IF false EXIT THEN
> >      debug-disk-label? IF
> >         ." Found " dos-logical-partitions .d ." logical partitions" cr
> > @@ -352,6 +359,7 @@ CONSTANT /gpt-part-entry
> >      no-mbr? IF drop FALSE EXIT THEN  \ read MBR and check for DOS disk-label magic
> >      count-dos-logical-partitions TO dos-logical-partitions
> > +   dos-logical-partitions 0= IF 0 EXIT THEN
> 
> Similar question here, what about the "addr" stack item? Shouldn't it be
> dropped first?
Yes. Will take a look at this too. Thanks!
I will make these both changes and test them out before sending out a
v3.

> 
>  Thomas
> 
> 
> PS: I'm still having trouble receiving your mail, I just discovered v2 on
> patchwork and downloaded it from there...
Okay I will check everything from my side to see if everything is in
order.
>
Kautuk Consul March 27, 2024, 5:47 a.m. UTC | #3
Hi Thomas,

I just sent out the v3. Can you please review that ?

Thanks again! :-)
diff mbox series

Patch

diff --git a/slof/fs/packages/disk-label.fs b/slof/fs/packages/disk-label.fs
index 661c6b0..2630701 100644
--- a/slof/fs/packages/disk-label.fs
+++ b/slof/fs/packages/disk-label.fs
@@ -132,11 +132,16 @@  CONSTANT /gpt-part-entry
    debug-disk-label? IF dup ." actual=" .d cr THEN
 ;
 
-\ read sector to array "block"
-: read-sector ( sector-number -- )
+\ read sector to array "block" and return actual bytes read
+: read-sector-ret ( sector-number -- actual-bytes )
    \ block-size is 0x200 on disks, 0x800 on cdrom drives
    block-size * 0 seek drop      \ seek to sector
-   block block-size read drop    \ read sector
+   block block-size read    \ read sector
+;
+
+\ read sector to array "block"
+: read-sector ( sector-number -- )
+   read-sector-ret drop
 ;
 
 : (.part-entry) ( part-entry )
@@ -204,7 +209,8 @@  CONSTANT /gpt-part-entry
          part-entry>sector-offset l@-le    ( current sector )
          dup to part-start to lpart-start  ( current )
          BEGIN
-            part-start read-sector          \ read EBR
+            part-start read-sector-ret          \ read EBR
+            block-size < IF UNLOOP 0 EXIT THEN
             1 partition>start-sector IF
                \ ." Logical Partition found at " part-start .d cr
                1+
@@ -279,6 +285,7 @@  CONSTANT /gpt-part-entry
    THEN
 
    count-dos-logical-partitions TO dos-logical-partitions
+   dos-logical-partitions 0= IF false EXIT THEN
 
    debug-disk-label? IF
       ." Found " dos-logical-partitions .d ." logical partitions" cr
@@ -352,6 +359,7 @@  CONSTANT /gpt-part-entry
    no-mbr? IF drop FALSE EXIT THEN  \ read MBR and check for DOS disk-label magic
 
    count-dos-logical-partitions TO dos-logical-partitions
+   dos-logical-partitions 0= IF 0 EXIT THEN
 
    debug-disk-label? IF
       ." Found " dos-logical-partitions .d ." logical partitions" cr