linux-kernel - [PATCH][next] mm/shmem: Fix check on uninitialized pointer 'folio'

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Message-Id: <20220504132135.229601-1-colin.i.king@gmail.com>
Date:   Wed,  4 May 2022 14:21:35 +0100
From:   Colin Ian King <colin.i.king@...il.com>
To:     Hugh Dickins <hughd@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: [PATCH][next] mm/shmem: Fix check on uninitialized pointer 'folio'

In the case where shmem_swapin returns null, the jump to the error return
path via label 'failed' will end up with the uninitialized pointer folio
being null checked a few statements later. Fix this by ensuring folio is
initialized to null.

Detected by clang scan:
mm/shmem.c:1704:7: warning: variable 'folio' is used uninitialized
whenever 'if' condition is true [-Wsometimes-uninitialized]

Fixes: 2b58b3f33ba2 ("mm/shmem: convert shmem_swapin_page() to shmem_swapin_folio()")
Signed-off-by: Colin Ian King <colin.i.king@...il.com>
---
 mm/shmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 107f1e4dd0aa..7faaa61ff7fa 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1682,7 +1682,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
 	struct shmem_inode_info *info = SHMEM_I(inode);
 	struct mm_struct *charge_mm = vma ? vma->vm_mm : NULL;
 	struct page *page;
-	struct folio *folio;
+	struct folio *folio = NULL;
 	swp_entry_t swap;
 	int error;
 
-- 
2.35.1