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[98.227.24.213]) by smtp.gmail.com with ESMTPSA id af79cd13be357-9366e03f05bsm26891485a.2.2026.08.06.16.43.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Aug 2026 16:43:13 -0700 (PDT) From: Frank Sorenson To: linux-cifs@vger.kernel.org, stfrench@microsoft.com, pc@manguebit.org Cc: stable@vger.kernel.org Subject: [PATCH 3/3] cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0 Date: Thu, 6 Aug 2026 18:43:06 -0500 Message-ID: <20260806234306.3662175-4-sorenson@redhat.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260806234306.3662175-1-sorenson@redhat.com> References: <20260806234306.3662175-1-sorenson@redhat.com> Precedence: bulk X-Mailing-List: linux-cifs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When cifs_remap_file_range() is called with len == 0 (the clone-to-EOF semantic), it computes the effective length as: len = src_inode->i_size - off; If off >= src_inode->i_size, this produces a negative loff_t that corrupts all downstream arithmetic: filemap_write_and_wait_range() is called with a wrapped range, and the ByteCount in the FSCTL_DUPLICATE_EXTENTS_TO_FILE buffer receives a huge value, potentially causing the server to attempt a multi-terabyte clone. There is already a check for off >= src_inode->i_size at the point where -EOPNOTSUPP is remapped to -EINVAL, but that is reached only after the ioctl has already been sent with the corrupted length. lock_two_nondirectories() is held at this point (i_rwsem write on both inodes), so i_size_read() is stable. Add an early bounds check inside the len == 0 branch and return -EINVAL via the unlock path if off is at or beyond EOF. Fixes: 04b38d601239 ("vfs: pull btrfs clone API to vfs layer") Cc: stable@vger.kernel.org Signed-off-by: Frank Sorenson --- fs/smb/client/cifsfs.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c index 2073b29ff969..bd4936711ced 100644 --- a/fs/smb/client/cifsfs.c +++ b/fs/smb/client/cifsfs.c @@ -1413,8 +1413,13 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off, */ lock_two_nondirectories(target_inode, src_inode); - if (len == 0) + if (len == 0) { + if (off >= i_size_read(src_inode)) { + rc = -EINVAL; + goto unlock; + } len = src_inode->i_size - off; + } cifs_dbg(FYI, "clone range\n"); -- 2.55.0