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[2403:580d:fda1::299]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-34f6b88d984sm2561639a91.3.2026.01.08.15.32.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 08 Jan 2026 15:32:05 -0800 (PST) Message-ID: <3a9648fa-49c2-4f07-84ee-50a1c7d7196f@suse.com> Date: Fri, 9 Jan 2026 10:02:00 +1030 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] btrfs: add missing ASSERT for system space_info in reserve_chunk_space To: Jiasheng Jiang , Chris Mason , David Sterba Cc: linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260108194502.653-1-jiashengjiangcool@gmail.com> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=wqu@suse.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNGFF1IFdlbnJ1byA8d3F1QHN1c2UuY29tPsLAlAQTAQgAPgIbAwULCQgHAgYVCAkKCwIE FgIDAQIeAQIXgBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXVgBQkQ/lqxAAoJEMI9kfOh Jf6o+jIH/2KhFmyOw4XWAYbnnijuYqb/obGae8HhcJO2KIGcxbsinK+KQFTSZnkFxnbsQ+VY fvtWBHGt8WfHcNmfjdejmy9si2jyy8smQV2jiB60a8iqQXGmsrkuR+AM2V360oEbMF3gVvim 2VSX2IiW9KERuhifjseNV1HLk0SHw5NnXiWh1THTqtvFFY+CwnLN2GqiMaSLF6gATW05/sEd V17MdI1z4+WSk7D57FlLjp50F3ow2WJtXwG8yG8d6S40dytZpH9iFuk12Sbg7lrtQxPPOIEU rpmZLfCNJJoZj603613w/M8EiZw6MohzikTWcFc55RLYJPBWQ+9puZtx1DopW2jOwE0EWdWB rwEIAKpT62HgSzL9zwGe+WIUCMB+nOEjXAfvoUPUwk+YCEDcOdfkkM5FyBoJs8TCEuPXGXBO Cl5P5B8OYYnkHkGWutAVlUTV8KESOIm/KJIA7jJA+Ss9VhMjtePfgWexw+P8itFRSRrrwyUf E+0WcAevblUi45LjWWZgpg3A80tHP0iToOZ5MbdYk7YFBE29cDSleskfV80ZKxFv6koQocq0 vXzTfHvXNDELAuH7Ms/WJcdUzmPyBf3Oq6mKBBH8J6XZc9LjjNZwNbyvsHSrV5bgmu/THX2n g/3be+iqf6OggCiy3I1NSMJ5KtR0q2H2Nx2Vqb1fYPOID8McMV9Ll6rh8S8AEQEAAcLAfAQY AQgAJgIbDBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXWBBQkQ/lrSAAoJEMI9kfOhJf6o cakH+QHwDszsoYvmrNq36MFGgvAHRjdlrHRBa4A1V1kzd4kOUokongcrOOgHY9yfglcvZqlJ qfa4l+1oxs1BvCi29psteQTtw+memmcGruKi+YHD7793zNCMtAtYidDmQ2pWaLfqSaryjlzR /3tBWMyvIeWZKURnZbBzWRREB7iWxEbZ014B3gICqZPDRwwitHpH8Om3eZr7ygZck6bBa4MU o1XgbZcspyCGqu1xF/bMAY2iCDcq6ULKQceuKkbeQ8qxvt9hVxJC2W3lHq8dlK1pkHPDg9wO JoAXek8MF37R8gpLoGWl41FIUb3hFiu3zhDDvslYM4BmzI18QgQTQnotJH8= In-Reply-To: <20260108194502.653-1-jiashengjiangcool@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2026/1/9 06:15, Jiasheng Jiang 写道: > In reserve_chunk_space(), btrfs_find_space_info() is called to retrieve > the space_info for the SYSTEM block group. However, the returned pointer > is immediately dereferenced by spin_lock(&info->lock) without validation. > > While the SYSTEM space_info is expected to be present during normal > operations, direct dereference without checking creates a risk of a > null pointer dereference. This deviates from the coding pattern seen > in peer functions like btrfs_chunk_alloc() where such returns are > validated with an ASSERT. > > Add an ASSERT() to ensure the pointer is valid before access, improving > code robustness and consistency with the rest of the block-group logic. If you know how system chunk works, you must understand without a system chunk a btrfs will never be mounted. The ASSERT() looks unnecessary to me. Thanks, Qu > > Signed-off-by: Jiasheng Jiang > --- > fs/btrfs/block-group.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c > index 08b14449fabe..f4229ee4f573 100644 > --- a/fs/btrfs/block-group.c > +++ b/fs/btrfs/block-group.c > @@ -4313,6 +4313,7 @@ static void reserve_chunk_space(struct btrfs_trans_handle *trans, > lockdep_assert_held(&fs_info->chunk_mutex); > > info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_SYSTEM); > + ASSERT(info); > spin_lock(&info->lock); > left = info->total_bytes - btrfs_space_info_used(info, true); > spin_unlock(&info->lock);