kdb: Fix the putarea helper function

stable inclusion
from stable-v5.10.110
commit e2a26253921920861f17fffcab1ec926807ad2ae
bugzilla: https://gitee.com/openeuler/kernel/issues/I574AL

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e2a26253921920861f17fffcab1ec926807ad2ae

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

[ Upstream commit c1cb8142 ]

Currently kdb_putarea_size() uses copy_from_kernel_nofault() to write *to*
arbitrary kernel memory. This is obviously wrong and means the memory
modify ('mm') command is a serious risk to debugger stability: if we poke
to a bad address we'll double-fault and lose our debug session.

Fix this the (very) obvious way.

Note that there are two Fixes: tags because the API was renamed and this
patch will only trivially backport as far as the rename (and this is
probably enough). Nevertheless Christoph's rename did not introduce this
problem so I wanted to record that!

Fixes: fe557319 ("maccess: rename probe_kernel_{read,write} to copy_{from,to}_kernel_nofault")
Fixes: 5d5314d6 ("kdb: core for kgdb back end (1 of 2)")
Signed-off-by: NDaniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: NDouglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20220128144055.207267-1-daniel.thompson@linaro.orgSigned-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYu Liao <liaoyu15@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

kernel/debug/kdb/kdb_support.c

@@ -350,7 +350,7 @@ int kdb_getarea_size(void *res, unsigned long addr, size_t size)
  */
 int kdb_putarea_size(unsigned long addr, void *res, size_t size)
 {
-	int ret = copy_from_kernel_nofault((char *)addr, (char *)res, size);
+	int ret = copy_to_kernel_nofault((char *)addr, (char *)res, size);
 	if (ret) {
 		if (!KDB_STATE(SUPPRESS)) {
 			kdb_printf("kdb_putarea: Bad address 0x%lx\n", addr);