Messages in this thread Patch in this message | | | Date | Tue, 14 Jun 2022 19:28:31 +0200 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH v1] sysfs: fix sysfs_kf_seq_show null pointer dereference |
| |
On Tue, Jun 14, 2022 at 05:24:01PM +0000, Will McVicker wrote: > When the kobj->ktype is null,
How can that happen? What in-tree code does that?
> sysfs_file_ops() returns a NULL pointer > for the sysfs_ops. When this happens, we hit a kernel panic in > sysfs_kf_seq_show() by dereferencing ops to check if ->show is NULL. > Based on commit 820879ee1865 ("sysfs: simplify sysfs_kf_seq_show"), it > sounds like we won't hit this often, but I have randomly hit this on my > Pixel 6 with 5.19-rc1. Refer to the crash stack below: > > Unable to handle kernel paging request at virtual address ... > Internal error: Oops: 96000004 [#1] PREEMPT SMP > Hardware name: Oriole EVT 1.0 (DT) > pc : sysfs_kf_seq_show+0x3c/0x160 > lr : kernfs_seq_show+0x54/0xa0 > Call trace: > sysfs_kf_seq_show+0x3c/0x160 > kernfs_seq_show+0x54/0xa0 > seq_read_iter+0x17c/0x638 > kernfs_fop_read_iter+0x70/0x1f4 > vfs_read+0x240/0x36c > ksys_read+0x7c/0xf0 > __arm64_sys_read+0x20/0x30 > invoke_syscall+0x60/0x150 > el0_svc_common+0xb8/0x100 > do_el0_svc+0x30/0xd4 > el0_svc+0x30/0xc0 > el0t_64_sync_handler+0x88/0xf8 > el0t_64_sync+0x1a0/0x1a4 > > Fixes: 820879ee1865 ("sysfs: simplify sysfs_kf_seq_show") > Signed-off-by: Will McVicker <willmcvicker@google.com> > --- > fs/sysfs/file.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c > index a12ac0356c69..f09f86f10410 100644 > --- a/fs/sysfs/file.c > +++ b/fs/sysfs/file.c > @@ -45,7 +45,7 @@ static int sysfs_kf_seq_show(struct seq_file *sf, void *v) > ssize_t count; > char *buf; > > - if (WARN_ON_ONCE(!ops->show)) > + if (WARN_ON_ONCE(!ops || !ops->show)) > return -EINVAL;
Seems reasonable, but I want to track down how ops can be NULL here under normal operation.
thanks,
greg k-h
| |