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[2403:580d:fda1::299]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b7127a0a2f9sm1696657a12.9.2025.10.25.03.06.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 25 Oct 2025 03:07:00 -0700 (PDT) Message-ID: <293c10e8-fa6b-4da2-8d7d-9eaf6b4ecd4b@suse.com> Date: Sat, 25 Oct 2025 20:36:56 +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 fs/btrfs] btrfs: fix memory leak of qgroup_list in btrfs_add_qgroup_relation To: Shardul Bankar , linux-btrfs@vger.kernel.org Cc: clm@fb.com, dsterba@suse.com, linux-kernel@vger.kernel.org References: <20251025092951.2866847-1-shardulsb08@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: <20251025092951.2866847-1-shardulsb08@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2025/10/25 19:59, Shardul Bankar 写道: > When btrfs_add_qgroup_relation() is called with invalid qgroup levels > (src >= dst), the function returns -EINVAL directly without freeing the > preallocated qgroup_list structure passed by the caller. This causes a > memory leak because the caller unconditionally sets the pointer to NULL > after the call, preventing any cleanup. > > The issue occurs because the level validation check happens before the > mutex is acquired and before any error handling path that would free > the prealloc pointer. On this early return, the cleanup code at the > 'out' label (which includes kfree(prealloc)) is never reached. > > In btrfs_ioctl_qgroup_assign(), the code pattern is: > > prealloc = kzalloc(sizeof(*prealloc), GFP_KERNEL); > ret = btrfs_add_qgroup_relation(trans, sa->src, sa->dst, prealloc); > prealloc = NULL; // Always set to NULL regardless of return value > ... > kfree(prealloc); // This becomes kfree(NULL), does nothing > > When the level check fails, 'prealloc' is never freed by either the > callee or the caller, resulting in a 64-byte memory leak per failed > operation. This can be triggered repeatedly by an unprivileged user > with access to a writable btrfs mount, potentially exhausting kernel > memory. > > Fix this by changing the early return to a goto that reaches the > cleanup code, ensuring prealloc is always freed on all error paths. > > Reported-by: BRF (btrfs runtime fuzzer) > Fixes: 8465ecec9611 ("btrfs: Check qgroup level in kernel qgroup assign.") > Signed-off-by: Shardul Bankar > --- > fs/btrfs/qgroup.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c > index 1175b8192cd7..0a25bfdd442f 100644 > --- a/fs/btrfs/qgroup.c > +++ b/fs/btrfs/qgroup.c > @@ -1539,8 +1539,10 @@ int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans, u64 src, u64 dst > ASSERT(prealloc); > > /* Check the level of src and dst first */ > - if (btrfs_qgroup_level(src) >= btrfs_qgroup_level(dst)) > - return -EINVAL; > + if (btrfs_qgroup_level(src) >= btrfs_qgroup_level(dst)) { > + ret = -EINVAL; > + goto out; > + } Out will call mutex_unlock(), but we haven't yet even locked the mutex. Please just call kfree(prealloc) then return. Thanks, Qu > > mutex_lock(&fs_info->qgroup_ioctl_lock); > if (!fs_info->quota_root) {