On Fri, Oct 05, 2018 at 05:32:07PM +0200, Dmitry Vyukov wrote: [...] > This all makes me think that somebody else has left these 0xf8 in > shadow before ext4_map_blocks started executing. > Unfortunately debugging garbage in stack shadow is not completely > trivial and there is no common recipe. I don't have setup to run arm64 > kernel at the moment. I would try to locate that garbage in stack > shadow earlier, e.g. calling another function before ext4_map_blocks, > implementing that function in mm/kasan/kasan.c (non-instrumented > itself) and then try to scan stack and verify presence of 0xf8 > garbage. If this works out, then try to catch garbage earlier and/or > try to figure out what function left that garbage (that's possible by > locating 0x41b58ab3 magic: > https://bugzilla.kernel.org/show_bug.cgi?id=198435). Thanks a lot for your analysis! I'll try to debug this further but as you pointed out it might be difficult to catch who writes beforehand to that location. --Jan
