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pstore: Add proper unregister lock checking

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The pstore backend lock wasn't being used during pstore_unregister().
Add sanity check and locking.

Link: https://lore.kernel.org/lkml/20200506152114.50375-7-keescook@chromium.org/
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2020-05-04 19:33:54 -07:00
parent db23491c77
commit 6248a0666c
1 changed files with 17 additions and 4 deletions
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21
fs/pstore/platform.c
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@ -69,8 +69,9 @@ static void pstore_dowork(struct work_struct *);
static DECLARE_WORK(pstore_work, pstore_dowork);
/*
* psinfo_lock just protects "psinfo" during
* calls to pstore_register()
* psinfo_lock protects "psinfo" during calls to
* pstore_register(), pstore_unregister(), and
* the filesystem mount/unmount routines.
*/
static DEFINE_MUTEX(psinfo_lock);
struct pstore_info *psinfo;
@ -587,8 +588,6 @@ int pstore_register(struct pstore_info *psi)
psinfo = psi;
mutex_init(&psinfo->read_mutex);
sema_init(&psinfo->buf_lock, 1);
mutex_unlock(&psinfo_lock);
if (psi->flags & PSTORE_FLAGS_DMESG)
allocate_buf_for_compression();
@ -620,12 +619,25 @@ int pstore_register(struct pstore_info *psi)
pr_info("Registered %s as persistent store backend\n", psi->name);
mutex_unlock(&psinfo_lock);
return 0;
}
EXPORT_SYMBOL_GPL(pstore_register);
void pstore_unregister(struct pstore_info *psi)
{
/* It's okay to unregister nothing. */
if (!psi)
return;
mutex_lock(&psinfo_lock);
/* Only one backend can be registered at a time. */
if (WARN_ON(psi != psinfo)) {
mutex_unlock(&psinfo_lock);
return;
}
/* Stop timer and make sure all work has finished. */
pstore_update_ms = -1;
del_timer_sync(&pstore_timer);
@ -644,6 +656,7 @@ void pstore_unregister(struct pstore_info *psi)
psinfo = NULL;
backend = NULL;
mutex_unlock(&psinfo_lock);
}
EXPORT_SYMBOL_GPL(pstore_unregister);