linux-kernel - [PATCH 2/3] mm: vmalloc: fix vmap_ram_vread

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Date:   Thu, 23 Mar 2023 12:58:35 +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>, Uladzislau Rezki <urezki@...il.com>,
        Christoph Hellwig <hch@...radead.org>,
        Baoquan He <bhe@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Andrey Konovalov <andreyknvl@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] mm: vmalloc: fix vmap_ram_vread_iter() return value

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

The error handling in vmap_ram_vread_iter() can return an
uninitialized value in some cases:

mm/vmalloc.c:3539:6: error: variable 'remains' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
        if (!vb)
            ^~~
mm/vmalloc.c:3587:17: note: uninitialized use occurs here
        return count - remains + zero_iter(iter, remains);
                       ^~~~~~~

Move the initialization up a few lines.

Fixes: d9cab54f7737 ("mm: vmalloc: convert vread() to vread_iter()")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 mm/vmalloc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index ebfa1e9fe6f9..fb216495fe5a 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3521,7 +3521,7 @@ static size_t vmap_ram_vread_iter(struct iov_iter *iter, const char *addr,
 	struct vmap_block *vb;
 	unsigned long offset;
 	unsigned int rs, re;
-	size_t remains, n;
+	size_t remains = count, n;
 
 	/*
 	 * If it's area created by vm_map_ram() interface directly, but
@@ -3545,7 +3545,6 @@ static size_t vmap_ram_vread_iter(struct iov_iter *iter, const char *addr,
 		goto finished_zero;
 	}
 
-	remains = count;
 	for_each_set_bitrange(rs, re, vb->used_map, VMAP_BBMAP_BITS) {
 		size_t copied;
 
-- 
2.39.2