nilfs2: fix possible int overflows in nilfs_fiemap()

Since nilfs_bmap_lookup_contig() in nilfs_fiemap() calculates its result
by being prepared to go through potentially maxblocks == INT_MAX blocks,
the value in n may experience an overflow caused by left shift of blkbits.

While it is extremely unlikely to occur, play it safe and cast right hand
expression to wider type to mitigate the issue.

Found by Linux Verification Center (linuxtesting.org) with static analysis
tool SVACE.

Link: https://lkml.kernel.org/r/20250124222133.5323-1-konishi.ryusuke@gmail.com
Fixes: 622daaff0a89 ("nilfs2: fiemap support")
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index e8015d24a82cde13ac3a79a5da0ea9b2d7f863ad..6613b8fcceb0d9c79b367f9614e35a37ef072012 100644 (file)
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -1186,7 +1186,7 @@ int nilfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
                        if (size) {
                                if (phys && blkphy << blkbits == phys + size) {
                                        /* The current extent goes on */
-                                       size += n << blkbits;
+                                       size += (u64)n << blkbits;
                                } else {
                                        /* Terminate the current extent */
                                        ret = fiemap_fill_next_extent(
@@ -1199,14 +1199,14 @@ int nilfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
                                        flags = FIEMAP_EXTENT_MERGED;
                                        logical = blkoff << blkbits;
                                        phys = blkphy << blkbits;
-                                       size = n << blkbits;
+                                       size = (u64)n << blkbits;
                                }
                        } else {
                                /* Start a new extent */
                                flags = FIEMAP_EXTENT_MERGED;
                                logical = blkoff << blkbits;
                                phys = blkphy << blkbits;
-                               size = n << blkbits;
+                               size = (u64)n << blkbits;
                        }
                        blkoff += n;
                }