Messages in this thread Patch in this message | | | Date | Tue, 18 Sep 2018 18:07:22 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [PATCH 14/33] vfs: Implement a filesystem superblock creation/configuration context [ver #11] |
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Hi,
On (09/11/18 16:54), Guenter Roeck wrote: > On Wed, Sep 12, 2018 at 12:17:35AM +0100, David Howells wrote: > > Guenter Roeck <linux@roeck-us.net> wrote: > > > > > [ 8.507672] RIP: 0010:reconfigure_super+0x47/0x210 > > > > Can you tell me the file and line this corresponds to? > > > I don't know, but some debugging shows that fc->ops == NULL.
This NULL derefs linux-next.
Emergency (sysrq remount/reboot):
emergency_remount() do_emergency_remount() do_emergency_remount_callback() reconfigure_super()
At fc->ops dereference:
981 if (fc->ops->reconfigure) { ^^^^^^^^^ 982 retval = fc->ops->reconfigure(fc); 983 if (retval == 0) { 984 security_sb_reconfigure(fc);
So the check either better be
if (fc->ops && fc->ops->reconfigure)
Or, we need to set ->ops properly. But I'm not sure if invoking ->init_fs_context() from emergency-reboot path is going to work well all the time.
---
fs/super.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/fs/super.c b/fs/super.c index efb0567c8389..e2e03c47c817 100644 --- a/fs/super.c +++ b/fs/super.c @@ -1017,6 +1017,7 @@ int reconfigure_super(struct fs_context *fc) static void do_emergency_remount_callback(struct super_block *sb) { struct fs_context fc = { + .ops = &legacy_fs_context_ops, .purpose = FS_CONTEXT_FOR_EMERGENCY_RO, .fs_type = sb->s_type, .root = sb->s_root, --- -ss
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