2013/3/1 Andy Lutomirski <luto@xxxxxxxxxxxxxx>: > [possible resend -- sorry] > > On 02/28/2013 07:25 AM, Pavel Shilovsky wrote: >> This patchset adds support of O_DENY* flags for Linux fs layer. These flags can be used by any application that needs share reservations to organize a file access. VFS already has some sort of this capability - now it's done through flock/LOCK_MAND mechanis, but that approach is non-atomic. This patchset build new capabilities on top of the existing one but doesn't bring any changes into the flock call semantic. >> >> These flags can be used by NFS (built-in-kernel) and CIFS (Samba) servers and Wine applications through VFS (for local filesystems) or CIFS/NFS modules. This will help when e.g. Samba and NFS server share the same directory for Windows and Linux users or Wine applications use Samba/NFS share to access the same data from different clients. >> >> According to the previous discussions the most problematic question is how to prevent situations like DoS attacks where e.g /lib/liba.so file can be open with DENYREAD, or smth like this. That's why one extra flag O_DENYMAND is added. It indicates to underlying layer that an application want to use O_DENY* flags semantic. It allows us not affect native Linux applications (that don't use O_DENYMAND flag) - so, these flags (and the semantic of open syscall that they bring) are used only for those applications that really want it proccessed that way. >> >> So, we have four new flags: >> O_DENYREAD - to prevent other opens with read access, >> O_DENYWRITE - to prevent other opens with write access, >> O_DENYDELETE - to prevent delete operations (this flag is not implemented in VFS and NFS part and only suitable for CIFS module), >> O_DENYMAND - to switch on/off three flags above. > > O_DENYMAND doesn't deny anything. Would a name like O_RESPECT_DENY be > better? > > Other than that, this seems like a sensible mechanism. I don't mind to rename it. Your suggestion looks ok to me, thanks. -- Best regards, Pavel Shilovsky. -- To unsubscribe from this list: send the line "unsubscribe linux-cifs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
