Re: linux-next: Tree for Jan 20 -- Kernel panic - Unable to mount root fs

On Wednesday, January 21, 2015 12:27:26 AM Sabrina Dubroca wrote: > 2015-01-20, 23:17:25 +0000, Al Viro wrote: > > On Tue, Jan 20, 2015 at 10:50:41PM +0000, Al Viro wrote: > > > doesn't look at _anything_ other than name->name other than for > > > audit_inode(). And name->name is apparently the same. > > > > > > It looks like something ends up buggering name->name in process, but > > > then > > > the damn thing appears to be normal after return from > > > filename_lookup()... > > > > If my reconstruction of what's going on is correct, the call chain here > > is do_path_lookup() <- kern_path() <- lookup_bdev() <- > > blkdev_get_by_path() > > <- mount_bdev() <- some_type.mount() <- mount_fs() > > <- vfs_kern_mount() <- do_new_mount() <- do_mount() <- sys_mount() > > <- do_mount_root() <- mount_block_root() <- mount_root(). Which is > > obscenely long, BTW, but that's a separate story... > > > > Could you slap > > > > struct stat buf; > > int n = sys_newstat(name, &buf); > > printk(KERN_ERR "stat(\"%s\") -> %d\n", name, n); > > n = sys_newstat("/dev", &buf); > > printk(KERN_ERR "stat(\"dev\") -> %d\n", n); > > > > in the beginning of mount_block_root() (init/do_mounts.c) and see what > > it > > prints? > > I get > > stat("/dev/root") -> -2 > stat("dev") -> -2 > with the patch applied (+panic) > > > and: > > stat("/dev/root") -> 0 > stat("dev") -> 0 > with the old version of do_path_lookup. Wait a minute ... at this early stage of boot, I'm pretty sure we don't have a valid current->audit_context since we haven't fork'd anything. If the audit context was non-NULL garbage that might explain the panic ...