From: Oleg Nesterov <oleg@xxxxxxxxxx> commit 013b2deba9a6b80ca02f4fafd7dedf875e9b4450 upstream. 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. Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx> Reviewed-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx> Acked-by: Christian Borntraeger <borntraeger@xxxxxxxxxx> Tested-by: Sven Schnelle <svens@xxxxxxxxxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/events/uprobes.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -612,10 +612,6 @@ static int prepare_uprobe(struct uprobe 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); @@ -911,6 +907,15 @@ static int __uprobe_register(struct inod 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); if (!uprobe) @@ -1708,6 +1713,9 @@ static int is_trap_at_addr(struct mm_str 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();
