tty fix fu_list abuse
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From: Christoph Hellwig on 7 Jul 2010 12:10 On Wed, Jul 07, 2010 at 10:25:10PM +1000, Nick Piggin wrote: > tty: fix fu_list abuse > > tty code abuses fu_list, which causes a bug in remount,ro handling. > > If a tty device node is opened on a filesystem, then the name unlinked, the > filesystem will be allowed to be remounted readonly. This is because > fs_may_remount_ro does not find the 0 link tty inode on the file sb list > (because the tty code incorrectly removed it to use for its own purpose). This > can result in a filesystem with errors after it is marked "clean". So add a > new private list for ttys and leave tty files on the sb list so they are caught > by this check. This makes tty nodes behave the same way as other device nodes. > > The next step is to allocate a tty private structure at private_data and get > rid of f_ttyonly_list, but the error handling is not trivial in the tty code. > Hence this intermediate step. Growing struct file by two pointers for the tty special case simply isn't acceptable. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Nick Piggin on 7 Jul 2010 12:20
On Wed, Jul 07, 2010 at 06:08:35PM +0200, Christoph Hellwig wrote: > On Wed, Jul 07, 2010 at 10:25:10PM +1000, Nick Piggin wrote: > > tty: fix fu_list abuse > > > > tty code abuses fu_list, which causes a bug in remount,ro handling. > > > > If a tty device node is opened on a filesystem, then the name unlinked, the > > filesystem will be allowed to be remounted readonly. This is because > > fs_may_remount_ro does not find the 0 link tty inode on the file sb list > > (because the tty code incorrectly removed it to use for its own purpose). This > > can result in a filesystem with errors after it is marked "clean". So add a > > new private list for ttys and leave tty files on the sb list so they are caught > > by this check. This makes tty nodes behave the same way as other device nodes. > > > > The next step is to allocate a tty private structure at private_data and get > > rid of f_ttyonly_list, but the error handling is not trivial in the tty code. > > Hence this intermediate step. > > Growing struct file by two pointers for the tty special case simply > isn't acceptable. I agree, so it can be removed when tty gets its act together. But tty breaks the s_files list right now which is not acceptable either. So I think it is better to take the simple fix that can be easily applied. I liked your patch, but error handling was totally broken in it so that indicates it is going to require some maturing in the tty tree. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |