Re: [PATCH] arch:powerpc simple_write_to_buffer return check

On 05/02/21 12:51 pm, Christophe Leroy wrote:

Please provide some description of the change.

And please clarify the patch subject, because as far as I can see, the return is already checked allthough the check seams wrong.

This was my first patch. I will try to provide better description of changes and subject in later patches.

Le 04/02/2021 à 19:16, Mayank Suman a écrit :

quoted

Signed-off-by: Mayank Suman <redacted>
---
  arch/powerpc/kernel/eeh.c                    | 8 ++++----
  arch/powerpc/platforms/powernv/eeh-powernv.c | 4 ++--
  2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kernel/eeh.c b/arch/powerpc/kernel/eeh.c
index 813713c9120c..2dbe1558a71f 100644
--- a/arch/powerpc/kernel/eeh.c
+++ b/arch/powerpc/kernel/eeh.c

@@ -1628,8 +1628,8 @@ static ssize_t eeh_force_recover_write(struct file *filp,

      char buf[20];
      int ret;
  -    ret = simple_write_to_buffer(buf, sizeof(buf), ppos, user_buf, count);
-    if (!ret)
+    ret = simple_write_to_buffer(buf, sizeof(buf)-1, ppos, user_buf, count);
+    if (ret <= 0) >           return -EFAULT;

Why return -EFAULT when the function has returned -EINVAL ?

If -EINVAL is returned by simple_write_to_buffer, we should return -EINVAL.

And why is it -EFAULT when ret is 0 ? EFAULT means error accessing memory.

The earlier check returned EFAULT when ret is 0. Most probably, there was an assumption
that writing 0 bytes (by simple_write_to_buffer) means a fault with memory (or error accessing memory).