linux-kernel - [PATCH 1/3] mm/mmap/vma_merge: actually set next to NULL if not applicable

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Date:   Thu, 23 Mar 2023 12:58:34 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Lorenzo Stoakes <lstoakes@...il.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Suren Baghdasaryan <surenb@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: [PATCH 1/3] mm/mmap/vma_merge: actually set next to NULL if not applicable

From: Arnd Bergmann <arnd@...db.de>

As clang builds point out, the variable 'next' is now uninitialized
in some conditions as a result of a previous patch that tried to
rely on it being NULL here:

mm/mmap.c:939:11: error: variable 'next' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
        else if (!curr)
                 ^~~~~
mm/mmap.c:952:15: note: uninitialized use occurs here
        merge_next = next && mpol_equal(policy, vma_policy(next)) &&
                     ^~~~

Fixes: e887ecae997e ("mm/mmap/vma_merge: set next to NULL if not applicable")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 mm/mmap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/mmap.c b/mm/mmap.c
index 54099a604cf8..c01d43bd694e 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -939,6 +939,8 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
 	else if (!curr)
 		/* Is there a VMA next to a hole (case 1 - 3) or prev (4)? */
 		next = vma_lookup(mm, end);
+	else
+		next = NULL;
 
 	/* Can we merge the predecessor? */
 	if (prev && addr == prev->vm_end && mpol_equal(vma_policy(prev), policy)
-- 
2.39.2