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Fri, 13 Mar 2026 05:37:16 -0700 (PDT) Received: from pve-server ([49.205.216.49]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2aece7edd1fsm30703505ad.47.2026.03.13.05.37.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Mar 2026 05:37:15 -0700 (PDT) From: Ritesh Harjani (IBM) To: Ye Bin , tytso@mit.edu, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org Cc: jack@suse.cz Subject: Re: [PATCH -next 8/8] ext4: fix possible null-ptr-deref in mbt_kunit_exit() In-Reply-To: <20260310130412.3156753-9-yebin@huaweicloud.com> Date: Fri, 13 Mar 2026 18:03:28 +0530 Message-ID: References: <20260310130412.3156753-1-yebin@huaweicloud.com> <20260310130412.3156753-9-yebin@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Ye Bin writes: > From: Ye Bin > > There's issue as follows: > # test_new_blocks_simple: failed to initialize: -12 > KASAN: null-ptr-deref in range [0x0000000000000638-0x000000000000063f] > Tainted: [E]=UNSIGNED_MODULE, [N]=TEST > RIP: 0010:mbt_kunit_exit+0x5e/0x3e0 [ext4_test] > Call Trace: > > kunit_try_run_case_cleanup+0xbc/0x100 [kunit] > kunit_generic_run_threadfn_adapter+0x89/0x100 [kunit] > kthread+0x408/0x540 > ret_from_fork+0xa76/0xdf0 > ret_from_fork_asm+0x1a/0x30 > > If mbt_kunit_init() init testcase failed will lead to null-ptr-deref. > So add test if 'sb' is inited success in mbt_kunit_exit(). > > Fixes: 7c9fa399a369 ("ext4: add first unit test for ext4_mb_new_blocks_simple in mballoc") > Signed-off-by: Ye Bin > --- > fs/ext4/mballoc-test.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/fs/ext4/mballoc-test.c b/fs/ext4/mballoc-test.c > index c75b91ae0cf0..90ed505fa4b1 100644 > --- a/fs/ext4/mballoc-test.c > +++ b/fs/ext4/mballoc-test.c > @@ -362,7 +362,6 @@ static int mbt_kunit_init(struct kunit *test) > return ret; > } > > - test->priv = sb; > kunit_activate_static_stub(test, > ext4_read_block_bitmap_nowait, > ext4_read_block_bitmap_nowait_stub); > @@ -383,6 +382,8 @@ static int mbt_kunit_init(struct kunit *test) > return -ENOMEM; > } > > + test->priv = sb; > + So, I see that "test" which is of "struct kunit" type, is always initialized locally on stack, so test->priv by default is always NULL. Hence this make sense to me. Feel free to add: Reviewed-by: Ritesh Harjani (IBM) > return 0; > } > > @@ -390,6 +391,9 @@ static void mbt_kunit_exit(struct kunit *test) > { > struct super_block *sb = (struct super_block *)test->priv; > > + if (!sb) > + return; > + > mbt_mb_release(sb); > mbt_ctx_release(sb); > mbt_ext4_free_super_block(sb); > -- > 2.34.1