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Date: Fri, 30 Dec 2011 16:26:49 -0800 From: Andrew Ayer <agwa@...rewayer.name> To: Alexander Viro <viro@...iv.linux.org.uk> Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org Subject: [PATCH 0/2] vfs: POSIX-compliant version of fchmodat with flag argument Hi, The below patches implement a 4 argument version of fchmodat (fchmodat4) that supports a flag argument, as specified by POSIX. Currently, the glibc wrapper has a flag argument, but fails with EOPNOTSUPP if you specify AT_SYMLINK_NOFOLLOW. POSIX says that fchmodat should only fail with EOPNOTSUPP if you specify AT_SYMLINK_NOFOLLOW and the path actually refers to a symbolic link (and the system doesn't support changing the mode of symbolic links). Unfortunately glibc can't do better because the current syscall doesn't have a flag argument. In addition to supporting AT_SYMLINK_NOFOLLOW, this also supports the AT_EMPTY_PATH flag, just like fchownat. Besides the POSIX-compliance, this patch will make it possible to ensure, in a race-free way, that you do not follow symlinks when chmodding. Previously, you could open a file with O_NOFOLLOW and fchmod it, but this only worked if you had read or write permissions on the file. Now you can open the file with O_PATH|O_NOFOLLOW and do fchmodat with AT_EMPTY_PATH. Any feedback is welcome. Cheers, Andrew -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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