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nilfs2: fix null-ptr-deref in block_dirty_buffer tracepoint

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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: 5305cb8308 ("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>
This commit is contained in:
Ryusuke Konishi 2024-11-07 01:07:33 +09:00 committed by Andrew Morton
parent cd45e963e4
commit 2026559a6c
4 changed files with 2 additions and 6 deletions
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2
fs/nilfs2/btnode.c
View File

@ -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);

4
fs/nilfs2/gcinode.c
View File

@ -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);

1
fs/nilfs2/mdt.c
View File

@ -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);

1
fs/nilfs2/page.c
View File

@ -63,6 +63,7 @@ struct buffer_head *nilfs_grab_buffer(struct inode *inode,
folio_put(folio);
return NULL;
}
bh->b_bdev = inode->i_sb->s_bdev;
return bh;
}