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?