Re: [PATCH] uprobes: ensure that uprobe->offset and ->ref_ctr_offset are properly aligned

[Srikar Dronamraju]

* Oleg Nesterov <oleg@xxxxxxxxxx> [2020-05-04 18:47:25]:

> 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: stable@xxxxxxxxxxxxxxx
> Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>

Thanks Oleg.

Looks good to me.

Reviewed-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
> ---


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Thanks and Regards
Srikar Dronamraju