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staging/lustre/libcfs: Properly handle debugfs read- and write-only files

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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@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Oleg Drokin 2016-02-06 02:01:50 -05:00 committed by Greg Kroah-Hartman
parent 5ba907a949
commit 49a76d7040
1 changed files with 25 additions and 2 deletions
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27
drivers/staging/lustre/lustre/libcfs/module.c
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@ -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,