On 2016/9/23 22:42, Tejun Heo wrote: > Hello, > > On Wed, Sep 21, 2016 at 12:19:53PM +0800, zijun_hu wrote: >> From: zijun_hu <zijun_hu@xxxxxxx> >> >> endless loop maybe happen if either of parameter addr and end is not >> page aligned for kernel API function ioremap_page_range() >> >> in order to fix this issue and alert improper range parameters to user >> WARN_ON() checkup and rounding down range lower boundary are performed >> firstly, loop end condition within ioremap_pte_range() is optimized due >> to lack of relevant macro pte_addr_end() >> >> Signed-off-by: zijun_hu <zijun_hu@xxxxxxx> > > Unfortunately, I can't see what the points are in this series of > patches. Most seem to be gratuitous changes which don't address real > issues or improve anything. "I looked at the code and realized that, > if the input were wrong, the function would misbehave" isn't good > enough a reason. What's next? Are we gonna harden all pointer taking > functions too? > > For internal functions, we don't by default do input sanitization / > sanity check. There sure are cases where doing so is beneficial but > reading a random function and thinking "oh this combo of parameters > can make it go bonkers" isn't the right approach for it. We end up > with cruft and code changes which nobody needed in the first place and > can easily introduce actual real bugs in the process. > > It'd be an a lot more productive use of time and effort for everyone > involved if the work is around actual issues. > > Thanks. > thanks for your reply firstly 1. ioremap_page_range() is not a kernel internal function 2. sanity check "BUG_ON(addr >= end)" have existed already, but don't check enough 3. are there any obvious hint for rang parameter requirements but BUG_ON(addr >= end) 4. if range which seems right but wrong really is used such as mapping virtual range [0x80000800, 0x80007800) to physical area[0x20000800, 0x20007800) what actions should we take? warning message and trying to finish user request or panic kernel or hang system in endless loop or return -EINVAL？ how to help user find their problem? 5. if both boundary of the range are aligned to page, ioremap_page_range() works well otherwise endless loop maybe happens -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>