arm64: kdump: update ppos when reading elfcorehdr

stable inclusion
from stable-5.10.27
commit 3db5fc556515e4676ee89f6736e0cf0c3e3c6072
bugzilla: 51493

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

[ 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: NChen Jun <chenjun102@huawei.com>
Acked-by: N  Weilong Chen <chenweilong@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/arm64/kernel/crash_dump.c

@@ -64,5 +64,7 @@ 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;
 }