Hi, On Mon, May 04, 2020 at 08:40:44PM +0200, Christian Borntraeger wrote: > > > On 04.05.20 18:47, Oleg Nesterov 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. > > I think the idea was that the uprobe instruction is 2 bytes and instructions > are always aligned to 2 bytes on s390. (we can have 2,4 or 6 bytes). > > > > > 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. > > Not sure if it would have been possible to try to create a uprobe on an > odd address. If yes, then the new IS_ALIGNED check certainly makes this > better for s390, so the patch looks sane. Adding Vasily and Sven to double > check.
I did a quick test, and without this patch it is possible to place a uprobe at an odd address. With the patch it fails with EINVAL, which is more reasonable. Regards Sven
