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Date: Thu, 30 Apr 2015 11:32:05 +0930 From: Rusty Russell <rusty@...tcorp.com.au> To: Gobinda Maji <gobinda.cemk07@...il.com> Cc: linux-next@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 9/9] sysfs: disallow world-writable files. Gobinda Maji <gobinda.cemk07@...il.com> writes: > Hi Rusty, Hi Gobinda, > I have a small doubt about the permission restriction (User perms >= > group perms >= other perms) in VERIFY_OCTAL_PERMISSIONS(). Please Note > that permission field of User, Group or Other consists of three bits. > LSB is EXECUTE permission, MSB is READ permission and the middle bit > is WRITE permission. Say for example, permission value is "0431". Here > User has only READ permission whereas Group has both WRITE and EXECUTE > permission and Other has EXECUTE permission. I guess, it is not good > to give Group the WRITE permission whereas User itself has no WRITE > permission. You're absolutely right, well spotted! The checks can be tightened. We don't really care about execute, but logically write is "more privileged" than read. Best to separate the tests; OTHER_WRITABLE <= GROUP_WRITABLE <= OWNER_WRITABLE and OTHER_READABLE <= GROUP_READABLE <= OWNER_READABLE. A patch would be welcome! Thanks, Rusty. -- 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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