linux-kernel - [PATCH][next] mm/vmalloc: Fix read of pointer area after it has been free'd

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Message-Id: <20210329170730.121943-1-colin.king@canonical.com>
Date:   Mon, 29 Mar 2021 18:07:30 +0100
From:   Colin King <colin.king@...onical.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Nicholas Piggin <npiggin@...il.com>, linux-mm@...ck.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] mm/vmalloc: Fix read of pointer area after it has been free'd

From: Colin Ian King <colin.king@...onical.com>

Currently the memory pointed to by area is being freed by the
free_vm_area call and then area->nr_pages is referencing the
free'd object. Fix this swapping the order of the warn_alloc
message and the free.

Addresses-Coverity: ("Read from pointer after free")
Fixes: 014ccf9b888d ("mm/vmalloc: improve allocation failure error messages")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 mm/vmalloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index b73e4e715e0d..7936405749e4 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2790,11 +2790,11 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
 	}
 
 	if (!pages) {
-		free_vm_area(area);
 		warn_alloc(gfp_mask, NULL,
 			   "vmalloc size %lu allocation failure: "
 			   "page array size %lu allocation failed",
 			   area->nr_pages * PAGE_SIZE, array_size);
+		free_vm_area(area);
 		return NULL;
 	}
 
-- 
2.30.2