arm64: kdump: update ppos when reading elfcorehdr

stable inclusion
from linux-4.19.184
commit df6f09cb7143be1f981f42ec363e5551c5d890c2

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

[ Upstream commit 141f8202 ]

The ppos points to a position in the old kernel memory (and in case of
arm64 in the crash kernel since elfcorehdr is passed as a segment). The
function should update the ppos by the amount that was read. This bug is
not exposed by accident, but other platforms update this value properly.
So, fix it in ARM64 version of elfcorehdr_read() as well.
Signed-off-by: NPavel Tatashin <pasha.tatashin@soleen.com>
Fixes: e62aaeac ("arm64: kdump: provide /proc/vmcore file")
Reviewed-by: NTyler Hicks <tyhicks@linux.microsoft.com>
Link: https://lore.kernel.org/r/20210319205054.743368-1-pasha.tatashin@soleen.comSigned-off-by: NWill Deacon <will@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>

arch/arm64/kernel/crash_dump.c

@@ -67,5 +67,7 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
 ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
 {
 	memcpy(buf, phys_to_virt((phys_addr_t)*ppos), count);
+	*ppos += count;
+
 	return count;
 }