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Sat, 07 Nov 2026 20:58:26 -0800 (PST) Received: from localhost.localdomain ([98.148.34.5]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-37265618e11sm2471388eec.7.2026.11.07.20.58.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 07 Nov 2026 20:58:25 -0800 (PST) From: Hungyu Lin To: jaegeuk@kernel.org, chao@kernel.org Cc: daehojeong@google.com, linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, dennylin0707@gmail.com Subject: [PATCH] f2fs: require inode ownership for ioctls that change per-file state Date: Sun, 8 Nov 2026 04:57:22 +0000 Message-ID: <20261108045722.12091-1-dennylin0707@gmail.com> X-Mailer: git-send-email 2.43.0 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 Content-Transfer-Encoding: 8bit F2FS_IOC_RELEASE_COMPRESS_BLOCKS, F2FS_IOC_RESERVE_COMPRESS_BLOCKS, F2FS_IOC_SET_PIN_FILE and F2FS_IOC_IO_PRIO change the state of the inode behind the file descriptor without checking who the caller is. Any user who can open a file, even read-only, can: - release its compressed blocks, after which writes to the file fail with -EPERM until the blocks are reserved again or the file is truncated to zero; - reserve released blocks again, which consumes free space; - pin it while it has no data blocks, after which writes that extend the file fail with -EIO; - unpin it, so that garbage collection may move blocks that a user of F2FS_IOC_SET_PIN_FILE expects to stay in place; - set its write I/O priority hint. F2FS_IOC_SET_PIN_FILE checked inode_owner_or_capable() when it was added. Commit aff7b628ac2d ("f2fs: set pin_file under CAP_SYS_ADMIN") replaced that with a CAP_SYS_ADMIN check, and commit b13bdf03bb80 ("f2fs: allow all the users to pin a file") then removed the CAP_SYS_ADMIN check, leaving the ioctl without any permission check. The atomic write ioctls require both FMODE_WRITE and inode_owner_or_capable(). Requiring FMODE_WRITE here would break f2fs_io, which releases and reserves compressed blocks through a read-only file descriptor, and Android, which releases them the same way. Require only inode_owner_or_capable(), as F2FS_IOC_SET_PIN_FILE originally did, so that only the owner or a caller with CAP_FOWNER can change this state. Users can still pin their own files. Fixes: b13bdf03bb80 ("f2fs: allow all the users to pin a file") Fixes: ef8d563f184e ("f2fs: introduce F2FS_IOC_RELEASE_COMPRESS_BLOCKS") Fixes: c75488fb4d82 ("f2fs: introduce F2FS_IOC_RESERVE_COMPRESS_BLOCKS") Fixes: 5f95c1812a65 ("f2fs: add ioctl to get IO priority hint") Cc: stable@vger.kernel.org Signed-off-by: Hungyu Lin --- fs/f2fs/file.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index e2c0f5083313..0730de36554a 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -3664,6 +3664,9 @@ static int f2fs_ioc_set_pin_file(struct file *filp, unsigned long arg) if (!pin && IS_DEVICE_ALIASING(inode)) return -EOPNOTSUPP; + if (!inode_owner_or_capable(file_mnt_idmap(filp), inode)) + return -EACCES; + ret = mnt_want_write_file(filp); if (ret) return ret; @@ -3982,6 +3985,9 @@ static int f2fs_ioc_io_prio(struct file *filp, unsigned long arg) if (!S_ISREG(inode->i_mode) || level >= F2FS_IOPRIO_MAX) return -EINVAL; + if (!inode_owner_or_capable(file_mnt_idmap(filp), inode)) + return -EACCES; + inode_lock(inode); F2FS_I(inode)->ioprio_hint = level; inode_unlock(inode); @@ -4235,6 +4241,9 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg) if (f2fs_readonly(sbi->sb)) return -EROFS; + if (!inode_owner_or_capable(file_mnt_idmap(filp), inode)) + return -EACCES; + ret = mnt_want_write_file(filp); if (ret) return ret; @@ -4430,6 +4439,9 @@ static int f2fs_reserve_compress_blocks(struct file *filp, unsigned long arg) if (f2fs_readonly(sbi->sb)) return -EROFS; + if (!inode_owner_or_capable(file_mnt_idmap(filp), inode)) + return -EACCES; + ret = mnt_want_write_file(filp); if (ret) return ret; -- 2.43.0