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Fri, 30 Oct 2026 01:14:01 -0700 (PDT) Received: from [172.16.0.229] ([159.196.52.54]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ae6e9b1506sm7446568a91.15.2026.10.30.01.13.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 30 Oct 2026 01:14:00 -0700 (PDT) Message-ID: Date: Fri, 30 Oct 2026 18:43:54 +1030 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] btrfs: reject zero num_stripes in the system chunk array To: Cheng Yongkang Cc: David Sterba , Chris Mason , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org References: <179328314071.648427.12527832319954042748@gmail.com> <6ad220fa-d6a0-4b4c-a313-a0cc052b8637@suse.com> <179334729054.2353588.12398743988940745859@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 FgIDAQIeAQIXgBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJq3ujyBQkUpLw5AAoJEMI9kfOh Jf6o8OIH/0mqW+TQM4m2x3hCsnK+oB4yJH1qnGvIhFF/Lhs48wI02sGh6/4aA0hkCDfd9LHQ +ci4FUepZ9y4VS01+oIExbg/8ytzGYTzLtb44jK2GBOBVSJkMiha6jp22XFt7WUkT/tvbreu WWdGsaJIRQaZChy7xsMI8lqQ2WdmluZJ4LT0wD3l/l6QU1ZseMGySebdY9sVOQEOJNV7Qj92 /KOAFNmeZshV/qDI8Iw1RTs6TvLqCcqmlZLCmJkYSVhT1RonWRren8xIRcFEgMe004IDnt7V qdQhk/nhTS9x9MBAhMRl0TTE1VKDLvVALsud3iZLrmmtYvwPApzGJk052f0m28vOwE0EWdWB rwEIAKpT62HgSzL9zwGe+WIUCMB+nOEjXAfvoUPUwk+YCEDcOdfkkM5FyBoJs8TCEuPXGXBO Cl5P5B8OYYnkHkGWutAVlUTV8KESOIm/KJIA7jJA+Ss9VhMjtePfgWexw+P8itFRSRrrwyUf E+0WcAevblUi45LjWWZgpg3A80tHP0iToOZ5MbdYk7YFBE29cDSleskfV80ZKxFv6koQocq0 vXzTfHvXNDELAuH7Ms/WJcdUzmPyBf3Oq6mKBBH8J6XZc9LjjNZwNbyvsHSrV5bgmu/THX2n g/3be+iqf6OggCiy3I1NSMJ5KtR0q2H2Nx2Vqb1fYPOID8McMV9Ll6rh8S8AEQEAAcLAfAQY AQgAJgIbDBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJq3ukKBQkUzDspAAoJEMI9kfOhJf6o SNsH/1ysUWOKmzY0rGS3ZdS61QgqMGhSWD/EJ4UiPw+xO4l4+GtX0fOAqxqsmBKqje3vyhBa Z5o/1Y+gNiN+E6RBcSz4b1TAd78sQ2bvT5DWOvBjeeVxHdiuQMIn4S8xk5ZpySBw5ifjoiuL 0M33UVtJOzM8yfAeL+d/Rp4leJw72SutjkLyZTG/gJIp4pJGD/kFHn24OLL0IxEcO0gOekNZ os5e1R6jAJ2ILk7+MDnvU8wXHcCiVzuDhJLI1tih1uUIE50muHQJWbYuVBbdJeu8WlIDDssx UOCxLylNG3gDXV5MhLubPTOpp9OiFc/XC37nvkgEcrlmlOFBv4/NJCbECpo= In-Reply-To: <179334729054.2353588.12398743988940745859@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2026/10/30 18:31, Cheng Yongkang 写道: > Hi Qu, > > Removing the ASSERT alone is not sufficient. btrfs_chunk_item_size() > computes > > sizeof(struct btrfs_chunk) + > sizeof(struct btrfs_stripe) * (num_stripes - 1) > > With num_stripes == 0, the (num_stripes - 1) term underflows in the > unsigned multiplication and the function returns 16 bytes (48 - 32) > instead of a valid item size. The system chunk array loop would then > advance by the wrong size before btrfs_check_chunk_valid() runs. > > So either btrfs_chunk_item_size() has to handle num_stripes == 0 first > (for example, return sizeof(struct btrfs_chunk) and let > btrfs_check_chunk_valid() reject it), or the early check has to stay so > the size calculation is never reached with zero stripes. I kept the > early check as the minimal fix; if you prefer centralizing the rejection > in the tree-checker, I can change btrfs_chunk_item_size() and drop the > check. Yes, drop the check and change btrfs_chunk_item_size() to handle zero num_stripes is not hard at all, and it's still smaller than your original fix: diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h index d5fe5cba0c35..891bc2432870 100644 --- a/fs/btrfs/volumes.h +++ b/fs/btrfs/volumes.h @@ -711,9 +711,8 @@ static inline enum btrfs_map_op btrfs_op(const struct bio *bio) static inline unsigned long btrfs_chunk_item_size(int num_stripes) { - ASSERT(num_stripes); - return sizeof(struct btrfs_chunk) + - sizeof(struct btrfs_stripe) * (num_stripes - 1); + return offsetof(struct btrfs_chunk, stripe) + + sizeof(struct btrfs_stripe) * num_stripes; } /* > > Thanks, > Cheng Yongkang