Hi Oleg, On Tue, May 5, 2020 at 12:47 AM Oleg Nesterov <o...@redhat.com> wrote: > > uprobe_write_opcode() must not cross page boundary; prepare_uprobe() > relies on arch_uprobe_analyze_insn() which should validate "vaddr" but > some architectures (csky, s390, and sparc) don't do this. > > We can remove the BUG_ON() check in prepare_uprobe() and validate the > offset early in __uprobe_register(). The new IS_ALIGNED() check matches > the alignment check in arch_prepare_kprobe() on supported architectures, > so I think that all insns must be aligned to UPROBE_SWBP_INSN_SIZE. > > Another problem is __update_ref_ctr() which was wrong from the very > beginning, it can read/write outside of kmap'ed page unless "vaddr" is > aligned to sizeof(short), __uprobe_register() should check this too. > > Cc: sta...@vger.kernel.org > Reported-by: Linus Torvalds <torva...@linux-foundation.org> > Suggested-by: Linus Torvalds <torva...@linux-foundation.org> > Signed-off-by: Oleg Nesterov <o...@redhat.com> > --- > kernel/events/uprobes.c | 16 ++++++++++++---- > 1 file changed, 12 insertions(+), 4 deletions(-) > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index ece7e13f6e4a..cc2095607c74 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -867,10 +867,6 @@ static int prepare_uprobe(struct uprobe *uprobe, struct > file *file, > if (ret) > goto out; > > - /* uprobe_write_opcode() assumes we don't cross page boundary */ > - BUG_ON((uprobe->offset & ~PAGE_MASK) + > - UPROBE_SWBP_INSN_SIZE > PAGE_SIZE); > - > smp_wmb(); /* pairs with the smp_rmb() in handle_swbp() */ > set_bit(UPROBE_COPY_INSN, &uprobe->flags); > > @@ -1166,6 +1162,15 @@ static int __uprobe_register(struct inode *inode, > loff_t offset, > if (offset > i_size_read(inode)) > return -EINVAL; > > + /* > + * This ensures that copy_from_page(), copy_to_page() and > + * __update_ref_ctr() can't cross page boundary. > + */ > + if (!IS_ALIGNED(offset, UPROBE_SWBP_INSN_SIZE)) > + return -EINVAL; > + if (!IS_ALIGNED(ref_ctr_offset, sizeof(short))) > + return -EINVAL; > + > retry: > uprobe = alloc_uprobe(inode, offset, ref_ctr_offset); > if (!uprobe) > @@ -2014,6 +2019,9 @@ static int is_trap_at_addr(struct mm_struct *mm, > unsigned long vaddr) > uprobe_opcode_t opcode; > int result; > > + if (WARN_ON_ONCE(!IS_ALIGNED(vaddr, UPROBE_SWBP_INSN_SIZE))) > + return -EINVAL; > + > pagefault_disable(); > result = __get_user(opcode, (uprobe_opcode_t __user *)vaddr); > pagefault_enable(); > -- > 2.25.1.362.g51ebf55 > > Looks good to me, thx.
Reviewed-by: Guo Ren <guo...@kernel.org> -- Best Regards Guo Ren ML: https://lore.kernel.org/linux-csky/
