On Wed, Nov 23, 2022 at 06:08:09PM +0000, Carlos Llamas wrote:
commit 3ce00bb7e91cf57d723905371507af57182c37ef upstream.
Since commit 1da52815d5f1 ("binder: fix alloc->vma_vm_mm null-ptr dereference") binder caches a pointer to the current->mm during open(). This fixes a null-ptr dereference reported by syzkaller. Unfortunately, it also opens the door for a process to update its mm after the open(), (e.g. via execve) making the cached alloc->mm pointer invalid.
Things get worse when the process continues to mmap() a vma. From this point forward, binder will attempt to find this vma using an obsolete alloc->mm reference. Such as in binder_update_page_range(), where the wrong vma is obtained via vma_lookup(), yet binder proceeds to happily insert new pages into it.
To avoid this issue fail the ->mmap() callback if we detect a mismatch between the vma->vm_mm and the original alloc->mm pointer. This prevents alloc->vm_addr from getting set, so that any subsequent vma_lookup() calls fail as expected.
Fixes: 1da52815d5f1 ("binder: fix alloc->vma_vm_mm null-ptr dereference") Reported-by: Jann Horn jannh@google.com Cc: stable@vger.kernel.org # 5.15+ Signed-off-by: Carlos Llamas cmllamas@google.com Acked-by: Todd Kjos tkjos@google.com Link: https://lore.kernel.org/r/20221104231235.348958-1-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org [cmllamas: renamed alloc->mm since missing e66b77e50522] Signed-off-by: Carlos Llamas cmllamas@google.com
drivers/android/binder_alloc.c | 7 +++++++ 1 file changed, 7 insertions(+)
This is already in the 6.0 queue, is this a different version?
thanks,
greg k-h