Return -EINVAL if whence is not understood by /dev/null or /dev/zero.
lseek() on /dev/null and /dev/zero always returns 0. This is
problematic for userland programs that detect holes and advancing the
offset by the calculated delta (SEEK_HOLE - SEEK_DATA), which will
always be calculated as zero.
Link: https://github.com/util-linux/util-linux/pull/4132
Signed-off-by: David Timber <dxdt@dev.snart.me>
---
drivers/char/mem.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index cca4529431f8..f0318e924db9 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -576,7 +576,19 @@ static ssize_t write_full(struct file *file, const char __user *buf,
*/
static loff_t null_lseek(struct file *file, loff_t offset, int orig)
{
- return file->f_pos = 0;
+ loff_t ret;
+
+ switch (orig) {
+ case SEEK_SET:
+ case SEEK_CUR:
+ case SEEK_END:
+ ret = file->f_pos = 0;
+ break;
+ default:
+ ret = -EINVAL;
+ }
+
+ return ret;
}
/*
--
2.53.0.1.ga224b40d3f.dirty