efi: fix potential NULL deref in efi_mem_reserve_persistent

stable inclusion
from stable-v5.10.168
commit 87d4ff18738fd71e7e3c10827c80257da6283697
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7URR4

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=87d4ff18738fd71e7e3c10827c80257da6283697

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

[ Upstream commit 966d47e1 ]

When iterating on a linked list, a result of memremap is dereferenced
without checking it for NULL.

This patch adds a check that falls back on allocating a new page in
case memremap doesn't succeed.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 18df7577 ("efi/memreserve: deal with memreserve entries in unmapped memory")
Signed-off-by: NAnton Gusev <aagusev@ispras.ru>
[ardb: return -ENOMEM instead of breaking out of the loop]
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: Nzhaoxiaoqiang11 <zhaoxiaoqiang11@jd.com>

drivers/firmware/efi/efi.c

@@ -982,6 +982,8 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
 	/* first try to find a slot in an existing linked list entry */
 	for (prsv = efi_memreserve_root->next; prsv; ) {
 		rsv = memremap(prsv, sizeof(*rsv), MEMREMAP_WB);
+		if (!rsv)
+			return -ENOMEM;
 		index = atomic_fetch_add_unless(&rsv->count, 1, rsv->size);
 		if (index < rsv->size) {
 			rsv->entry[index].base = addr;