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

JIRA: https://issues.redhat.com/browse/RHEL-83630

commit 088f294
Author: Jiri Olsa <jolsa@kernel.org>
Date:   Fri Nov 22 00:11:18 2024 +0100

    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: stable@vger.kernel.org
    Cc: Alexander Gordeev <agordeev@linux.ibm.com>
    Fixes: 3d5854d ("fs/proc/kcore.c: allow translation of physical memory addresses")
    Signed-off-by: Jiri Olsa <jolsa@kernel.org>
    Link: https://lore.kernel.org/r/20241121231118.3212000-1-jolsa@kernel.org
    Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
    Signed-off-by: Christian Brauner <brauner@kernel.org>

Signed-off-by: Lichen Liu <lichliu@redhat.com>

Author: licliu

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.