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[2403:580d:fda1::299]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b25ca51aefsm82227135ad.16.2026.04.01.02.08.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 01 Apr 2026 02:08:20 -0700 (PDT) Message-ID: <4259c965-af46-4fb6-b7b6-514e11f34bc8@suse.com> Date: Wed, 1 Apr 2026 19:38:14 +1030 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] btrfs: fix double free in create_space_info() error path To: Guangshuo Li Cc: Chris Mason , David Sterba , Jiasheng Jiang , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260401031339.1418417-1-lgs201920130244@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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit > > So the call chain I had in mind is: > > `create_space_info()` > -> `btrfs_sysfs_add_space_info_type()` > -> `kobject_init_and_add()` > -> failure > -> `kobject_put(&space_info->kobj)` > -> `space_info_release()` > -> `kfree(space_info)` > > and then control returns to `create_space_info()`: > > `btrfs_sysfs_add_space_info_type()` returns error > -> `goto out_free` > -> `kfree(space_info)` Please add those two parts into the changelog. Otherwise the current one fix is good to me, for this particular call site. > > So my concern was that after `kobject_init_and_add()` has been called, > the cleanup is already handed to `kobject_put()` / > `space_info_release()`, and the later `kfree(space_info)` in > `create_space_info()` becomes a second free. > > If my understanding of the `kobject_init_and_add()` failure path here > is incorrect, please let me know. I may be missing something. Furthermore, there is a similar bug in create_space_info_sub_group() and all other locations. Personally speaking, I do not like the idea of releasing the space_info through the callback at all. It breaks the common scheme where who allocates the memory should free it, now we have different handling before and after kobject_init_and_add(), which is causing all kinds of problems. But I'm afraid that's the way we have to go. Thanks, Qu > > Thanks, > Guangshuo > > Qu Wenruo 于2026年4月1日周三 12:34写道： >> >> >> >> 在 2026/4/1 13:43, Guangshuo Li 写道: >>> When kobject_init_and_add() fails, btrfs_sysfs_add_space_info_type() >>> calls kobject_put(&space_info->kobj). >>> >>> The kobject release callback space_info_release() frees space_info, >>> but the current error path in create_space_info() then calls >>> kfree(space_info) again, causing a double free. >> >> Can you give an example call chain of where such space_info_release() is >> triggered? >> >>> >>> Keep the direct kfree(space_info) for the earlier failure path, but >>> after btrfs_sysfs_add_space_info_type() has called kobject_put(), let >>> the kobject release callback handle the cleanup. >>> >>> Fixes: a11224a016d6d ("btrfs: fix memory leaks in create_space_info() error paths") >>> Cc: stable@vger.kernel.org >>> Signed-off-by: Guangshuo Li >>> --- >>> fs/btrfs/space-info.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c >>> index 3f08e450f796..d7176eb2fcbf 100644 >>> --- a/fs/btrfs/space-info.c >>> +++ b/fs/btrfs/space-info.c >>> @@ -311,7 +311,7 @@ static int create_space_info(struct btrfs_fs_info *info, u64 flags) >>> >>> ret = btrfs_sysfs_add_space_info_type(space_info); >>> if (ret) >>> - goto out_free; >>> + return ret; >>> >>> list_add(&space_info->list, &info->space_info); >>> if (flags & BTRFS_BLOCK_GROUP_DATA) >>