Messages in this thread | | | From | (Eric W. Biederman) | Date | Fri, 15 May 2020 13:16:59 -0500 | Subject | Re: linux-next boot error: general protection fault in tomoyo_get_local_path |
| |
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> writes:
> This is > > if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/') { > char *ep; > const pid_t pid = (pid_t) simple_strtoul(pos + 1, &ep, 10); > struct pid_namespace *proc_pidns = proc_pid_ns(d_inode(dentry)); // <= here > > if (*ep == '/' && pid && pid == > task_tgid_nr_ns(current, proc_pidns)) { > > which was added by commit c59f415a7cb6e1e1 ("Use proc_pid_ns() to get pid_namespace from the proc superblock"). > > @@ -161,9 +162,10 @@ static char *tomoyo_get_local_path(struct dentry *dentry, char * const buffer, > if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/') { > char *ep; > const pid_t pid = (pid_t) simple_strtoul(pos + 1, &ep, 10); > + struct pid_namespace *proc_pidns = proc_pid_ns(d_inode(dentry)); > > if (*ep == '/' && pid && pid == > - task_tgid_nr_ns(current, sb->s_fs_info)) { > + task_tgid_nr_ns(current, proc_pidns)) { > pos = ep - 5; > if (pos < buffer) > goto out; > > Alexey and Eric, any clue?
Looking at the stack backtrace this is happening as part of creating a file or a device node. The dentry that is passed in most likely comes from d_alloc_parallel. So we have d_inode == NULL.
I want to suggest doing the very simple fix:
- if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/') { + if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/' && denty->d_inode) {
But I don't know if there are any other security hooks early in lookup, that could be called for an already existing dentry.
So it looks like we need a version proc_pid_ns that works for a dentry, or a superblock.
Alex do you think you can code up an patch against my proc-next branch to fix this?
Eric
| |