On Mon, Jun 24, 2019 at 7:50 PM Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > > On Mon, Jun 24, 2019 at 04:32:52PM +0200, Andrey Konovalov wrote: > > This patch is a part of a series that extends kernel ABI to allow to pass > > tagged user pointers (with the top byte set to something else other than > > 0x00) as syscall arguments. > > > > In copy_mount_options a user address is being subtracted from TASK_SIZE. > > If the address is lower than TASK_SIZE, the size is calculated to not > > allow the exact_copy_from_user() call to cross TASK_SIZE boundary. > > However if the address is tagged, then the size will be calculated > > incorrectly. > > > > Untag the address before subtracting. > > > > Reviewed-by: Khalid Aziz <khalid.aziz@xxxxxxxxxx> > > Reviewed-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx> > > Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> > > Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx> > > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> > > --- > > fs/namespace.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/fs/namespace.c b/fs/namespace.c > > index 7660c2749c96..ec78f7223917 100644 > > --- a/fs/namespace.c > > +++ b/fs/namespace.c > > @@ -2994,7 +2994,7 @@ void *copy_mount_options(const void __user * data) > > * the remainder of the page. > > */ > > /* copy_from_user cannot cross TASK_SIZE ! */ > > - size = TASK_SIZE - (unsigned long)data; > > + size = TASK_SIZE - (unsigned long)untagged_addr(data); > > if (size > PAGE_SIZE) > > size = PAGE_SIZE; > > I think this patch needs an ack from Al Viro (cc'ed). > > -- > Catalin Hi Al, Could you take a look and give your acked-by? Thanks!
