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/zL/cWUE+u021V/DBbV0OZeqy2vyGT89O6W7S4LV+QOOkzqjzqWyoSFKaXMfLS9BHcaNlRke66C iHKFUyOGsOJgmGtzq2sj+rUW6k9emK4lsa8L3gOF6c1O1nRU984EeaYDdl9bT8Q0inQZ8X63nfD 1Md2GB8OXKtzIXcCeb4pGiwJxM2CFH6eYSG7Y8yKf1kUtCacxId8GYAGWraIONYqDQ+s5d6gEvs 6ejhYT7k4iM6foJW5BvKPD1VebvZ+5NnjG4URuQr9f4p3r5VrMmqw44MrD8kaqhXHWevCKW3K8d NKpIwSQimohffS1+JPyaNdlSOzm3iWDnU8ErOHrJyq/6MGKlDhYPaxOsr+rn4HGkCCBK9WgTLET 7imBNY854Np0wUx65a7dTi1w6Pcm+scnteRjCaroNStkqDxXX43JsLPFfqkDp6h+PfwuGoby X-Authority-Analysis: v=2.4 cv=U9ySDfru c=1 sm=1 tr=0 ts=687783f6 b=1 cx=c_pps a=e1sVV491RgrpLwSTMOnk8w==:117 a=e1sVV491RgrpLwSTMOnk8w==:17 a=6eWqkTHjU83fiwn7nKZWdM+Sl24=:19 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=wKuvFiaSGQ0qltdbU6+NXLB8nM8=:19 a=Ol13hO9ccFRV9qXi2t6ftBPywas=:19 a=xqWC_Br6kY4A:10 a=kj9zAlcOel0A:10 a=Wb1JkmetP80A:10 a=GoEa3M9JfhUA:10 a=1XWaLZrsAAAA:8 a=cMq8TJlj-K9RFVth140A:9 a=CjuIK1q_8ugA:10 cc=ntf awl=host:13600 On Wed, Jul 16, 2025 at 12:44:23PM +0200, David Hildenbrand wrote: > On 16.07.25 05:05, Suren Baghdasaryan wrote: > > The /proc/pid/maps file is generated page by page, with the mmap_lock > > released between pages. This can lead to inconsistent reads if the > > underlying vmas are concurrently modified. For instance, if a vma split > > or merge occurs at a page boundary while /proc/pid/maps is being read, > > the same vma might be seen twice: once before and once after the change. > > This duplication is considered acceptable for userspace handling. > > However, observing a "hole" where a vma should be (e.g., due to a vma > > being replaced and the space temporarily being empty) is unacceptable. > > > > Implement a test that: > > 1. Forks a child process which continuously modifies its address space, > > specifically targeting a vma at the boundary between two pages. > > 2. The parent process repeatedly reads the child's /proc/pid/maps. > > 3. The parent process checks the last vma of the first page and > > the first vma of the second page for consistency, looking for the > > effects of vma splits or merges. > > > > The test duration is configurable via the -d command-line parameter > > in seconds to increase the likelihood of catching the race condition. > > The default test duration is 5 seconds. > > > > Example Command: proc-maps-race -d 10 > > > > Signed-off-by: Suren Baghdasaryan > > Why is this selftest not making use of any kselftest framework? > > I'm sure there is a very good reason :) > > Reading assert() feels very weird compared to other selftests. Sorry to meta-review via your review again David :P But just to say tools/testing/selftests/kselftest_harness.h is really good, and makes life simple. See tools/testing/selftests/mm/guard-regions.c for an example of how they can be used - pretty straightforward and avoids a lot of kselftest boilerplate. > > -- > Cheers, > > David / dhildenb > >