* Michael Keyes <mgkeyes@xxxxxxxxxxxxxxxxxxxx> [230430 18:41]: > On 29.04.23 15:32, Tad wrote: > > This reintroduces the issue described in > > https://lore.kernel.org/linux-mm/cb8dc31a-fef2-1d09-f133-e9f7b9f9e77a@xxxxxxxx/ > Yes, I also ran into this (even though I'd somehow missed it the > previous time). Rick Edgecombe reported something similar [1]. This is probably to do with my stack guard checks I recently added. > > Apparently the issue arises at mm/mmap.c:1582, where low_limit is set to > vm_end_gap(tmp). Occasionally, this returns a 64-bit address (e.g. > 0x7fedea581000), which is obviously greater than high_limit for a 32-bit > mmap, and causes the next call to mas_empty_area() to fail. > > I'm not sure why vm_end_gap(tmp) occasionally returns a 64-bit address, > or if the best solution is to just check for this and skip the retry if > it occurs… > Thanks for the debugging. I will look into it. I am currently trying to revise how the iterators, prev/next deal with shifting outside the requested limits. I suspect it's something to do with hitting the limit and what someone would assume the next operation means. [1] https://lore.kernel.org/linux-mm/32f156ba80010fd97dbaf0a0cdfc84366608624d.camel@xxxxxxxxx/
