[RFC/PATCH 1/2] pstore: Protect unlink with read_mutex

From: Namhyung Kim
Date: Tue Oct 18 2016 - 21:24:16 EST


When update_ms is set, pstore_get_records() will be called when there's
a new entry. But unlink can be called at the same time and might
contend with the open-read-close loop. Depending on the implementation
of platform driver, it may be safe or not. But I think it'd be better
to protect those race in the first place.

Cc: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
fs/pstore/inode.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index 1781dc50762e..75728dfae0a6 100644
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -197,11 +197,14 @@ static int pstore_unlink(struct inode *dir, struct dentry *dentry)
if (err)
return err;

- if (p->psi->erase)
+ if (p->psi->erase) {
+ mutex_lock(&p->psi->read_mutex);
p->psi->erase(p->type, p->id, p->count,
d_inode(dentry)->i_ctime, p->psi);
- else
+ mutex_unlock(&p->psi->read_mutex);
+ } else {
return -EPERM;
+ }

return simple_unlink(dir, dentry);
}
--
2.9.3