On Fri, 22 Mar 2024 10:42:47 +0530 Dev Jain <dev.jain@xxxxxxx> wrote: > > On 3/22/24 03:21, Andrew Morton wrote: > > On Thu, 21 Mar 2024 16:05:22 +0530 Dev Jain <dev.jain@xxxxxxx> wrote: > > > >> Currently, VA exhaustion is being checked by passing a hint to mmap() and > >> expecting it to fail. This patch makes a stricter test by successful write() > >> calls from /proc/self/maps to a dump file, confirming that a free chunk is > >> indeed not available. > > What's wrong with the current approach? > While populating the lower VA space, mmap() fails because we have > exhausted the space. > > Then, in validate_lower_address_hint(), because mmap() fails, we confirm > that we have > > indeed exhausted the space. There is a circular logic involved here. > > Assume that there is a bug in mmap(), also assume that it exists > independent of whether > > you pass a hint address or not; that for some reason it is not able to > find a 1GB chunk. > > My idea is to assert the exhaustion against some other method. Thanks. I added the above to the changelog. > > Also, in the following line in validate_complete_va_space(): > > if (start_addr - prev_end_addr >= SZ_1GB) > > I made a small error, I forgot to use MAP_CHUNK_SIZE instead of SZ_1GB. And the preceding comment might need an edit. Please send an updated patch?
