Commit 013b2deb authored May 04, 2020 by Oleg Nesterov Committed by Linus Torvalds Jun 09, 2020

uprobes: ensure that uprobe->offset and ->ref_ctr_offset are properly aligned



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@linux-foundation.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Tested-by: Sven Schnelle <svens@linux.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 8b4d37db

kernel/events/uprobes.c

+12 −4

Original line number	Diff line number	Diff line
		@@ -861,10 +861,6 @@ 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);

		@@ -1160,6 +1156,15 @@ 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)
		@@ -2008,6 +2013,9 @@ 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();

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