From: Oleg Drokin <green@xxxxxxxxxxxxxx>
It turns out that unlike procfs, debugfs does not really enforce
permissions for root (similar to regular filesystems), so we need
to ensure we are not providing ->write() method to read-only files
and ->read() method for write-only files at registration.
This fixes a couple of crashes on unexpected access.
Signed-off-by: Oleg Drokin <green@xxxxxxxxxxxxxx>
---
drivers/staging/lustre/lustre/libcfs/module.c | 27 +++++++++++++++++++++++++--
1 file changed, 25 insertions(+), 2 deletions(-)
diff --git a/drivers/staging/lustre/lustre/libcfs/module.c b/drivers/staging/lustre/lustre/libcfs/module.c
index d5a047b..611607a 100644
--- a/drivers/staging/lustre/lustre/libcfs/module.c
+++ b/drivers/staging/lustre/lustre/libcfs/module.c
@@ -502,13 +502,36 @@ static ssize_t lnet_debugfs_write(struct file *filp, const char __user *buf,
return error;
}
-static const struct file_operations lnet_debugfs_file_operations = {
+static const struct file_operations lnet_debugfs_file_operations_rw = {
.open = simple_open,
.read = lnet_debugfs_read,
.write = lnet_debugfs_write,
.llseek = default_llseek,
};
+static const struct file_operations lnet_debugfs_file_operations_ro = {
+ .open = simple_open,
+ .read = lnet_debugfs_read,
+ .llseek = default_llseek,
+};
+
+static const struct file_operations lnet_debugfs_file_operations_wo = {
+ .open = simple_open,
+ .write = lnet_debugfs_write,
+ .llseek = default_llseek,
+};
+
+static const struct file_operations *lnet_debugfs_fops_select(umode_t mode)
+{
+ if (!(mode & S_IWUGO))
+ return &lnet_debugfs_file_operations_ro;
+
+ if (!(mode & S_IRUGO))
+ return &lnet_debugfs_file_operations_wo;
+
+ return &lnet_debugfs_file_operations_rw;
+}
+
void lustre_insert_debugfs(struct ctl_table *table,
const struct lnet_debugfs_symlink_def *symlinks)
{
@@ -525,7 +548,7 @@ void lustre_insert_debugfs(struct ctl_table *table,
for (; table->procname; table++)
debugfs_create_file(table->procname, table->mode,
lnet_debugfs_root, table,
- &lnet_debugfs_file_operations);
+ lnet_debugfs_fops_select(table->mode));
for (; symlinks && symlinks->name; symlinks++)
debugfs_create_symlink(symlinks->name, lnet_debugfs_root,
--
2.1.0
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