On 2016/9/23 22:42, Tejun Heo wrote:

Hello,

On Wed, Sep 21, 2016 at 12:19:53PM +0800, zijun_hu wrote:

quoted

From: zijun_hu <redacted>

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 <redacted>

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 -EINVALi 1/4 ?
   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


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