On 4/19/22 05:59, Kees Cook wrote: > On Mon, Apr 18, 2022 at 09:22:11PM +0800, He Zhe wrote: >> This function checks if the given address range crosses frame boundary. >> It is based on the existing x86 algorithm, but implemented via stacktrace. >> This can be tested by USERCOPY_STACK_FRAME_FROM and >> USERCOPY_STACK_FRAME_TO in lkdtm. > Hi, > > Thanks for doing this implementation! One reason usercopy hardening > didn't persue doing a "full" stacktrace was because it seemed relatively > expensive. Did you do any usercopy-heavily workload testing to see if > there was a noticeable performance impact? > > It would be nice to block the exposure of canaries and PAC bits, though, > so I'm not opposed, but I'd like to get a better sense of how "heavy" > this might be. I just did some rough tests: hackbench -s 512 -l 200 -g 15 -f 25 -P Such line would hit arch_within_stack_frames at least 5000 times in my environment. With hardened_usercopy=on, the execution time would be around 2.121 seconds(average for 30 times) With hardened_usercopy=off, the execution time would be around 2.011 seconds(average for 30 times) I'll test the original x86 way for arm64 tomorrow. Any other workload needed to be run? Thanks, Zhe > > Thanks! > > -Kees >
