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 28a726553318b0e2203f5f139070fef6bdb3765e..1ced5bc551e491d56c9ccd361ce3bcdf43742c69 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 b0077f5f71124021c06d7db89af94b627e18392c..518e10be10736558ecb37855aca07a8f0ca28f75 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 e80ef2c0a785c493f59f604c74d681d5aec6233d..c1f9649164897b48d55993ddb26d64e59641df05 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 3efc0b39c20d2f2667f79037e4f3dbf2e79f9b54..d2d6d5c761e8db60931562c02058e6d32d0ecac5 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;
 }