Re: PowerPC: Random memory corruption causing kernel oops on Power11

[Paul Moore]

On Fri, May 29, 2026 at 12:18 PM David Laight
<david.laight.linux@xxxxxxxxx> wrote:
> On Fri, 29 May 2026 19:07:22 +0530
> Venkat Rao Bagalkote <venkat88@xxxxxxxxxxxxx> wrote:
> > On 29/05/26 12:20 pm, Venkat Rao Bagalkote wrote:
> > > Greetings!!!
> > >
> > > Kernel 7.1.0-rc5-next-20260528 crashes randomly on IBM Power11
> > > hardware. Attached is the config file.
> > >
> .
> >
> > Git bisect is pointing to 54067bacb49c selinux: hooks: use __getname()
> > to allocate path buffer as the first bad commit.
> >
> >
> > # git bisect good
> > 54067bacb49caeada82b20b6bd706dca0cb99ffc is the first bad commit
> > commit 54067bacb49caeada82b20b6bd706dca0cb99ffc
> > Author: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
> > Date:   Wed May 20 11:18:56 2026 +0300
> >
> >      selinux: hooks: use __getname() to allocate path buffer
> >
> >      selinux_genfs_get_sid() allocates memory for a path with
> > __get_free_page()
> >      although there is a dedicated helper for allocation of file paths:
> >      __getname().
> >
> >      Replace __get_free_page() for allocation of a path buffer with
> > __getname().
> >
> >      Signed-off-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
> >      Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>
> >
> >   security/selinux/hooks.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
>
> __getname() is kmalloc(PATH_MAX) aka kmalloc(4096).
>
> The old code was:
>         buffer = (char *)__get_free_page(GFP_KERNEL);
>         if (!buffer)
>                 return -ENOMEM;
>
>         path = dentry_path_raw(dentry, buffer, PAGE_SIZE);
> only the allocate was changed.
>
> PAGE_SIZE is not the length of the buffer.
> Should be PATH_MAX.

Yes, as discussed earlier in the thread some additional work needs to
be done, and verified, but since we are at the end of -rc5 I simply
reverted the patch.  We can chase this down next dev cycle.

-- 
paul-moore.com