Re: [PATCH mm-hotfixes] mm/vma: remove __vma_check_mmap_hook()

[Shinichiro Kawasaki]

On Apr 13, 2026 / 11:57, Lorenzo Stoakes wrote:
> Commit c50ca15dd496 ("mm: add vm_ops->mapped hook") introduced
> __vma_check_mmap_hook() in order to assert that a driver doesn't
> incorrectly implement both an f_op->mmap() and a vm_ops->mapped hook, the
> latter of which would not ultimately get invoked.
> 
> However, this did not correctly account for stacked drivers (or drivers
> that otherwise use the compatibility layer) which might recursively call
> an mmap_prepare hook via the compatibility layer.
> 
> Thus the nested mmap_prepare() invocation might result in a VMA which has
> vm_ops->mapped set with an overlaying mmap() hook, causing the
> __vma_check_mmap_hook() to fail in vfs_mmap(), wrongly failing the
> operation.
> 
> This patch resolves this by simply removing the check, as we can't be
> certain that an mmap() hook doesn't at some point invoke the compatibility
> layer, and it's not worth trying to track it.
> 
> Fixes: c50ca15dd496 ("mm: add vm_ops->mapped hook")
> Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>
> Closes: https://lore.kernel.org/all/adx2ws5z0NMIe5Yj@shinmob/
> Signed-off-by: Lorenzo Stoakes <ljs@xxxxxxxxxx>

Lorenzo, thank you for the swift fix. I applied this patch on top of the
next-20260410 kernel, and confirmed the failure disappeared. Good.

Tested-by: Shinichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>