linux-kernel - [PATCH 5.18 113/181] s390/crash: add missing iterator advance in copy_oldmem

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Date:   Mon, 27 Jun 2022 13:21:26 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Alexander Egorenkov <egorenar@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.18 113/181] s390/crash: add missing iterator advance in copy_oldmem_page()

From: Alexander Gordeev <agordeev@...ux.ibm.com>

[ Upstream commit cc02e6e21aa5f2ac0defe8c15e5a9d024da6e73d ]

In case old memory was successfully copied the passed iterator
should be advanced as well. Currently copy_oldmem_page() is
always called with single-segment iterator. Should that ever
change - copy_oldmem_user and copy_oldmem_kernel() functions
would need a rework to deal with multi-segment iterators.

Fixes: 5d8de293c224 ("vmcore: convert copy_oldmem_page() to take an iov_iter")
Reviewed-by: Alexander Egorenkov <egorenar@...ux.ibm.com>
Tested-by: Alexander Egorenkov <egorenar@...ux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@...ux.ibm.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/s390/kernel/crash_dump.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/s390/kernel/crash_dump.c b/arch/s390/kernel/crash_dump.c
index a2c1c55daec0..2534a31d2550 100644
--- a/arch/s390/kernel/crash_dump.c
+++ b/arch/s390/kernel/crash_dump.c
@@ -219,6 +219,11 @@ ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn, size_t csize,
 	unsigned long src;
 	int rc;
 
+	if (!(iter_is_iovec(iter) || iov_iter_is_kvec(iter)))
+		return -EINVAL;
+	/* Multi-segment iterators are not supported */
+	if (iter->nr_segs > 1)
+		return -EINVAL;
 	if (!csize)
 		return 0;
 	src = pfn_to_phys(pfn) + offset;
@@ -228,6 +233,8 @@ ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn, size_t csize,
 		rc = copy_oldmem_user(iter->iov->iov_base, src, csize);
 	else
 		rc = copy_oldmem_kernel(iter->kvec->iov_base, src, csize);
+	if (!rc)
+		iov_iter_advance(iter, csize);
 	return rc;
 }
 
-- 
2.35.1