nilfs2: fix possible int overflows in nilfs_fiemap()

commit 6438ef381c183444f7f9d1de18f22661cba1e946 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 97c1beb00637d87539b8858c6c268eaa529c3136..f328bb7e226689592c2ca2a16a202c107e0ee793 100644 (file)
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -1265,7 +1265,7 @@ 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(
@@ -1278,14 +1278,14 @@ 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;
                }