linux-kernel - [PATCH] bcachefs: Fix null-ptr-deref in bch2_fs

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Date: Mon, 4 Mar 2024 11:22:03 +0800
From: Li Zetao <lizetao1@...wei.com>
To: <kent.overstreet@...ux.dev>, <bfoster@...hat.com>
CC: <lizetao1@...wei.com>, <linux-bcachefs@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH] bcachefs: Fix null-ptr-deref in bch2_fs_alloc()

There is a null-ptr-deref issue reported by kasan:

  KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
  Call Trace:
    <TASK>
    bch2_fs_alloc+0x1092/0x2170 [bcachefs]
    bch2_fs_open+0x683/0xe10 [bcachefs]
    ...

When initializing the name of bch_fs, it needs to dynamically alloc memory
to meet the length of the name. However, when name allocation failed, it
will cause a null-ptr-deref access exception in subsequent string copy.

Fix this issue by checking if name allocation is successful.

Fixes: 401ec4db6308 ("bcachefs: Printbuf rework")
Signed-off-by: Li Zetao <lizetao1@...wei.com>
---
 fs/bcachefs/super.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c
index 6b23e11825e6..24fa41bbe7e3 100644
--- a/fs/bcachefs/super.c
+++ b/fs/bcachefs/super.c
@@ -818,13 +818,13 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
 		goto err;
 
 	pr_uuid(&name, c->sb.user_uuid.b);
-	strscpy(c->name, name.buf, sizeof(c->name));
-	printbuf_exit(&name);
-
 	ret = name.allocation_failure ? -BCH_ERR_ENOMEM_fs_name_alloc : 0;
 	if (ret)
 		goto err;
 
+	strscpy(c->name, name.buf, sizeof(c->name));
+	printbuf_exit(&name);
+
 	/* Compat: */
 	if (le16_to_cpu(sb->version) <= bcachefs_metadata_version_inode_v2 &&
 	    !BCH_SB_JOURNAL_FLUSH_DELAY(sb))
-- 
2.34.1