On Tue, Jun 11, 2019 at 4:38 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > On Sat, Jun 8, 2019 at 6:02 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > > > On Mon, Jun 03, 2019 at 06:55:10PM +0200, Andrey Konovalov wrote: > > > This patch is a part of a series that extends arm64 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: Catalin Marinas <catalin.marinas@xxxxxxx> > > > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> > > > > One thing I just noticed in the commit titles... "arm64" is in the > > prefix, but these are arch-indep areas. Should the ", arm64" be left > > out? > > > > I would expect, instead: > > > > fs/namespace: untag user pointers in copy_mount_options > > Hm, I've added the arm64 tag in all of the patches because they are > related to changes in arm64 kernel ABI. I can remove it from all the > patches that only touch common code if you think that it makes sense. I'll keep the arm64 tags in commit titles for v17. Please reply explicitly if you think I should remove them. Thanks! :) > > Thanks! > > > > > Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> > > > > -Kees > > > > > --- > > > fs/namespace.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/fs/namespace.c b/fs/namespace.c > > > index b26778bdc236..2e85712a19ed 100644 > > > --- a/fs/namespace.c > > > +++ b/fs/namespace.c > > > @@ -2993,7 +2993,7 @@ 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; > > > > > > -- > > > 2.22.0.rc1.311.g5d7573a151-goog > > > > > > > -- > > Kees Cook
