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[2403:580d:fda1::299]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-34a47c184bdsm77582a91.2.2025.12.08.12.19.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 08 Dec 2025 12:19:12 -0800 (PST) Message-ID: Date: Tue, 9 Dec 2025 06:49:06 +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: Optimize the timing of prealloc memory allocation To: Edward Adam Davis , syzbot+b44d4a4885bc82af2a06@syzkaller.appspotmail.com Cc: clm@fb.com, dsterba@suse.com, josef@toxicpanda.com, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com References: <693683ba.a70a0220.38f243.0091.GAE@google.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 在 2025/12/8 21:35, Edward Adam Davis 写道: > Too many abnormal exits can cause the prealloc assertion to fail, as > reported by syzbot in [1]. > > Move the prealloc memory allocation to before it is actually used. > > [1] > assertion failed: prealloc == NULL :: 0, in fs/btrfs/qgroup.c:3529 > kernel BUG at fs/btrfs/qgroup.c:3529! > Call Trace: > > create_subvol+0x5ad/0x18f0 fs/btrfs/ioctl.c:570 > btrfs_mksubvol+0x6e4/0x12c0 fs/btrfs/ioctl.c:928 > __btrfs_ioctl_snap_create+0x2b2/0x730 fs/btrfs/ioctl.c:1201 > btrfs_ioctl_snap_create+0x131/0x180 fs/btrfs/ioctl.c:1259 > btrfs_ioctl+0xb4d/0xd00 fs/btrfs/ioctl.c:-1 There is already a full revert, and your fix misses all the other error cases. https://lore.kernel.org/linux-btrfs/20251208195407.GC4859@twin.jikos.cz/T/#t > > Fixes: 252877a87015 ("btrfs: add ASSERTs on prealloc in qgroup functions") > Reported-by: syzbot+b44d4a4885bc82af2a06@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=b44d4a4885bc82af2a06 > Tested-by: syzbot+b44d4a4885bc82af2a06@syzkaller.appspotmail.com > Signed-off-by: Edward Adam Davis > --- > fs/btrfs/qgroup.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c > index 9e2b53e90dcb..ac5380520152 100644 > --- a/fs/btrfs/qgroup.c > +++ b/fs/btrfs/qgroup.c > @@ -3289,10 +3289,6 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid, > if (!btrfs_qgroup_enabled(fs_info)) > return 0; > > - prealloc = kzalloc(sizeof(*prealloc), GFP_NOFS); > - if (!prealloc) > - return -ENOMEM; > - > /* > * There are only two callers of this function. > * > @@ -3388,6 +3384,12 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid, > } > } > > + prealloc = kzalloc(sizeof(*prealloc), GFP_NOFS); > + if (!prealloc) { > + ret = -ENOMEM; > + goto out; > + } > + > spin_lock(&fs_info->qgroup_lock); > > dstgroup = add_qgroup_rb(fs_info, prealloc, objectid);