On Fri, 19 Jul 2024 13:21:30 +0200 David Hildenbrand <david@xxxxxxxxxx> > On 19.07.24 00:51, syzbot wrote: > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: 4d145e3f830b Merge tag 'i2c-for-6.10-rc8' of git://git.ker.. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=11321495980000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=6b5a15443200e31 > > dashboard link: https://syzkaller.appspot.com/bug?extid=ec4b7d82bb051330f15a > > compiler: aarch64-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 > > userspace arch: arm64 > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=113e054e980000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1366ab85980000 > > > > The reproducer involves udmabuf. I suspect it has to do with it. > > But I'm curius, does the reproducer not trigger before 4d145e3f830b on > mainliny? > > Viveks changes are not upstream yet, but I can only speculate that we > have some issue similar to the one we had with hugetlb: udmabuf doing > things with memfd/shmem pages that it shouldn't do, because it doesn't > "own" these pages. > > "udmabuf: Use vmf_insert_pfn and VM_PFNMAP for handling mmap" might help. cpu1 cpu2 --- --- evict() find folio2 in page cache truncate_inode_folio() truncate_cleanup_folio(); // unmap folio2 from mmA unmap_mapping_folio(folio2); mmap folio2 to mmB filemap_remove_folio(folio2); If the window exists for mapping folio to userspace while indoe is evicted, is this report false positive?
