On Wed, Mar 20, 2024 at 11:26:07AM -0700, Max Filippov wrote: > In NUMMU kernel the value of linux_binprm::p is the offset inside the > temporary program arguments array maintained in separate pages in the > linux_binprm::page. linux_binprm::exec being a copy of linux_binprm::p > thus must be adjusted when that array is copied to the user stack. > Without that adjustment the value passed by the NOMMU kernel to the ELF > program in the AT_EXECFN entry of the aux array doesn't make any sense > and it may break programs that try to access memory pointed to by that > entry. > > Adjust linux_binprm::exec before the successful return from the > transfer_args_to_stack(). What's the best way to test this? (Is there a qemu setup I can use to see the before/after of AT_EXECFN?) How did you encounter the problem? > > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Max Filippov <jcmvbkbc@xxxxxxxxx> > --- > fs/exec.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/fs/exec.c b/fs/exec.c > index af4fbb61cd53..5ee2545c3e18 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -895,6 +895,7 @@ int transfer_args_to_stack(struct linux_binprm *bprm, > goto out; > } > > + bprm->exec += *sp_location - MAX_ARG_PAGES * PAGE_SIZE; > *sp_location = sp; > > out: > -- > 2.39.2 > -- Kees Cook
