linux-kernel - [PATCH] efi: fix potential NULL deref in efi_mem_reserve

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Date:   Fri,  3 Feb 2023 16:22:13 +0300
From:   Anton Gusev <aagusev@...ras.ru>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Anton Gusev <aagusev@...ras.ru>,
        Jonathan Richardson <jonathan.richardson@...adcom.com>,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        lvc-project@...uxtesting.org
Subject: [PATCH] efi: fix potential NULL deref in efi_mem_reserve_persistent

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: 18df7577adae ("efi/memreserve: deal with memreserve entries in unmapped memory")
Signed-off-by: Anton Gusev <aagusev@...ras.ru>
---
 drivers/firmware/efi/efi.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index a2b0cbc8741c..48d30c806d94 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -1007,6 +1007,8 @@ 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)
+			break;
 		index = atomic_fetch_add_unless(&rsv->count, 1, rsv->size);
 		if (index < rsv->size) {
 			rsv->entry[index].base = addr;
-- 
2.39.1