On Wed, May 17, 2023 at 12:40:03AM -0700, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 065efa589871 Add linux-next specific files for 20230517 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=17f27bb2280000 > kernel config: https://syzkaller.appspot.com/x/.config?x=821eeb02ef201bcc > dashboard link: https://syzkaller.appspot.com/bug?extid=ac3b41786a2d0565b6d5 > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/dbbd691e9e5a/disk-065efa58.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/e5b9541c3979/vmlinux-065efa58.xz > kernel image: https://storage.googleapis.com/syzbot-assets/44cf3f3aaabb/bzImage-065efa58.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+ac3b41786a2d0565b6d5@xxxxxxxxxxxxxxxxxxxxxxxxx > > ================================================================================ > UBSAN: array-index-out-of-bounds in kernel/pid.c:244:15 Only way I see this happening is if the logic in kernel/pid_namespace.c:create_pid_cachep() which sets the object size for the struct pid allocation of this pid namespace based on parent_pid_namespace->level + 1 is broken. The way this works is: struct pid { [snip] struct upid numbers[1]; }; create_pid_namespace() { unsigned int level = parent_pid_ns->level + 1; ns->pid_cachep = create_pid_cachep(level); } and then during fork: alloc_pid() { pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL); } So effectively, the wrong level must've been set in create_pid_namespace() so that the flexible array allocation is too small. I don't have time to debug this tbh. Ccing Kees maybe there's some flexible array stuff going on I'm unaware of.
