fs/proc/kcore.c: Clear ret value in read_kcore_iter after successful iov_iter_zero

If iov_iter_zero succeeds after failed copy_from_kernel_nofault,
we need to reset the ret value to zero otherwise it will be returned
as final return value of read_kcore_iter.

This fixes objdump -d dump over /proc/kcore for me.

Cc: [email protected]
Cc: Alexander Gordeev <[email protected]>
Fixes: 3d5854d ("fs/proc/kcore.c: allow translation of physical memory addresses")
Signed-off-by: Jiri Olsa <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Acked-by: Alexander Gordeev <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>

Author: olsajiri

fs/proc/kcore.c

@@ -600,6 +600,7 @@ static ssize_t read_kcore_iter(struct kiocb *iocb, struct iov_iter *iter)
 					ret = -EFAULT;
 					goto out;
 				}
+				ret = 0;
 			/*
 			 * We know the bounce buffer is safe to copy from, so
 			 * use _copy_to_iter() directly.