nilfs2: fix null-ptr-deref in block_dirty_buffer tracepoint

commit 2026559a6c4ce34db117d2db8f710fe2a9420d5a upstream.

When using the "block:block_dirty_buffer" tracepoint, mark_buffer_dirty()
may cause a NULL pointer dereference, or a general protection fault when
KASAN is enabled.

This happens because, since the tracepoint was added in
mark_buffer_dirty(), it references the dev_t member bh->b_bdev->bd_dev
regardless of whether the buffer head has a pointer to a block_device
structure.

In the current implementation, nilfs_grab_buffer(), which grabs a buffer
to read (or create) a block of metadata, including b-tree node blocks,
does not set the block device, but instead does so only if the buffer is
not in the "uptodate" state for each of its caller block reading
functions.  However, if the uptodate flag is set on a folio/page, and the
buffer heads are detached from it by try_to_free_buffers(), and new buffer
heads are then attached by create_empty_buffers(), the uptodate flag may
be restored to each buffer without the block device being set to
bh->b_bdev, and mark_buffer_dirty() may be called later in that state,
resulting in the bug mentioned above.

Fix this issue by making nilfs_grab_buffer() always set the block device
of the super block structure to the buffer head, regardless of the state
of the buffer's uptodate flag.

Link: https://lkml.kernel.org/r/20241106160811.3316-3-konishi.ryusuke@gmail.com
Fixes: 5305cb830834 ("block: add block_{touch|dirty}_buffer tracepoint")
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Ubisectech Sirius <bugreport@valiantsec.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/btnode.c b/fs/nilfs2/btnode.c
index 19ed9015bd660655d092da3721e1e42aea1956d4..13d943df871dd08a5909ff8b9ff71b161c65974b 100644 (file)
--- a/fs/nilfs2/btnode.c
+++ b/fs/nilfs2/btnode.c
@@ -68,7 +68,6 @@ nilfs_btnode_create_block(struct address_space *btnc, __u64 blocknr)
                goto failed;
        }
        memset(bh->b_data, 0, i_blocksize(inode));
-       bh->b_bdev = inode->i_sb->s_bdev;
        bh->b_blocknr = blocknr;
        set_buffer_mapped(bh);
        set_buffer_uptodate(bh);
@@ -133,7 +132,6 @@ int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
                goto found;
        }
        set_buffer_mapped(bh);
-       bh->b_bdev = inode->i_sb->s_bdev;
        bh->b_blocknr = pblocknr; /* set block address for read */
        bh->b_end_io = end_buffer_read_sync;
        get_bh(bh);

diff --git a/fs/nilfs2/gcinode.c b/fs/nilfs2/gcinode.c
index fcd13da5d0125d250d0a5b6d1e7aefc0055be57a..2f612288ea4517b829679e7446c599fdc2ff0ee4 100644 (file)
--- a/fs/nilfs2/gcinode.c
+++ b/fs/nilfs2/gcinode.c
@@ -83,10 +83,8 @@ int nilfs_gccache_submit_read_data(struct inode *inode, sector_t blkoff,
                goto out;
        }
 
-       if (!buffer_mapped(bh)) {
-               bh->b_bdev = inode->i_sb->s_bdev;
+       if (!buffer_mapped(bh))
                set_buffer_mapped(bh);
-       }
        bh->b_blocknr = pbn;
        bh->b_end_io = end_buffer_read_sync;
        get_bh(bh);

diff --git a/fs/nilfs2/mdt.c b/fs/nilfs2/mdt.c
index cbf4fa60eea217f44d81ac9ca2832aad2b065057..d0808953296ac884f1ac35d9e7aa582478c480fb 100644 (file)
--- a/fs/nilfs2/mdt.c
+++ b/fs/nilfs2/mdt.c
@@ -89,7 +89,6 @@ static int nilfs_mdt_create_block(struct inode *inode, unsigned long block,
        if (buffer_uptodate(bh))
                goto failed_bh;
 
-       bh->b_bdev = sb->s_bdev;
        err = nilfs_mdt_insert_new_block(inode, block, bh, init_block);
        if (likely(!err)) {
                get_bh(bh);

diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c
index 0854b786a513d4bf81bb5d8fe1ea4b19d0c1fd3a..b4e2192e87967f97e917c4a945ebfa6ace195808 100644 (file)
--- a/fs/nilfs2/page.c
+++ b/fs/nilfs2/page.c
@@ -63,6 +63,7 @@ struct buffer_head *nilfs_grab_buffer(struct inode *inode,
                put_page(page);
                return NULL;
        }
+       bh->b_bdev = inode->i_sb->s_bdev;
        return bh;
 }