[PATCH 0/4] fs: ubifs: Fix crash and add safeguards

[Heiko Schocher]

Hello Alexander,

On 03.07.24 12:12, Alexander Dahl wrote:
> Hei hei,
> 
> filesystem handling is different in U-Boot and beyond that UBI/UBIFS is
> different from other filesystems in U-Boot.  There's UBI and UBIFS code
> ported from Linux (quite old already now, maybe someone wants to update
> that?), and there's "glue code" or "wrapper code" to interface with
> U-Boot scripts, commands, and filesystem handling.  The fixes and
> improvements in this patch series are for this U-Boot specific glue
> code.

Yes, the linux base is very old ... patches are welcome!

And for me it is not that easy, as I do not have a hardware with
current mainline U-Boot running on it... I want to update a hardware
I have to current mainline, but I had no time yet for it...

> I'm no filesystem expert, but after days of debugging I'm quite sure the
> bug is in U-Boot since UBIFS support was added in 2009, and it was
> repeated in 2015 when generic filesystem support for UBIFS was added.
> So please review carefully!

Which bug?

> The crashes were not easily reproducible, only with boards using the old
> distroboot _and_ a boot script inspired by (but not equal to) the one
> proposed by RAUC [1], which basically boils down to:
> 
>    ubifsmount ubi0:boot (from distroboot)
>    test -e (from distroboot)
>    ubifsmount ubi0:rootfs1 (this time from the boot script,
>                             triggering a ubifs_umount)

So, you have a special sequence you execute to trigger the bug, good!

In special 2 ubifsmount in a row... may not often needed for booting!
(I ask me, why that is needed? Boottime is not good than...)

BTW: Is this really a good bootcmd in [1] as on *every* boot your
      Environment is saved? This is not good for lifetime of your
      storage device ... why not using bootcounter?

> Crashes can be triggered more easily, if patch order is changed and
> patch 2 (resetting pointers to NULL after free) comes first, or if patch
> 2 is applied on its own only.

Hmm...

> The fix is in the first patch, and on my boards I see no crashes
> anymore.  I also tested all kinds of combinations of calling `ubi part`,
> `ubi detach`, `ubifsmount`, `ubifsumount`, `ubifsls`, `ubifsload`, `ls`,
> `load`, `size`, and `test -e` and got no crashes anymore after the fix.

That sounds good! Hmm.. test -e has nothing to do with ubi/ubifs I think.

On what hardware do you test? Is it in mainline?

> The three additional patches (2 to 4) are more or less safeguards and
> improvements for the future, and come from me trying and my debugging
> code done on the way, more or less optional, but I think nice to have.

I will look at them .. but give me some time, as I am in holidays the
next 2 weeks ... Hmm.. and it would be good to get some Tested-by
from people with hardware...

bye,
Heiko
> 
> Greets
> Alex
> 
> [1] https://github.com/rauc/rauc/blob/master/contrib/uboot.sh
> 
> Alexander Dahl (4):
>    fs: ubifs: Fix memleak and double free in u-boot wrapper functions
>    fs: ubifs: Set pointers to NULL after free
>    fs: ubifs: Make k(z)alloc/kfree symmetric
>    fs: ubifs: Add volume mounted check
> 
>   fs/ubifs/super.c |  8 ++++++--
>   fs/ubifs/ubifs.c | 31 +++++++++++++++++++------------
>   2 files changed, 25 insertions(+), 14 deletions(-)
> 
> 
> base-commit: 65fbdab27224ee3943a89496b21862db83c34da2
> 

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