6.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Morduan Zang <redacted>

commit d7f1b4bdc7108be1b178e1617b5f45c8918e88d7 upstream.

The return value calculation was incorrect: `return len - buf_size;`
Initially `len = buf_size`, then `len` decreases with each operation.
This results in a negative return value on success.

Fix by returning `buf_size - len` which correctly calculates the actual
number of bytes written.

Fixes: a976d790f494 ("efi/cper: Add a new helper function to print bitmasks")
Signed-off-by: Morduan Zang <redacted>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/firmware/efi/cper.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/firmware/efi/cper.c
+++ b/drivers/firmware/efi/cper.c

@@ -162,7 +162,7 @@ int cper_bits_to_str(char *buf, int buf_
 		len -= size;
 		str += size;
 	}
-	return len - buf_size;
+	return buf_size - len;
 }
 EXPORT_SYMBOL_GPL(cper_bits_to_str);