[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. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/