Messages in this thread | | | Date | Mon, 26 Jul 2010 11:49:31 +0200 | From | Andi Kleen <> | Subject | Re: [PATCH] Fix off-by-one bug in mbind() syscall implementation |
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On Mon, Jul 26, 2010 at 11:28:18AM +0200, Andre Przywara wrote: > When the mbind() syscall implementation processes the node mask > provided by the user, the last node is accidentally masked out. > This is present since the dawn of time (aka Before Git), I guess > nobody realized that because libnuma as the most prominent user of > mbind() uses large masks (sizeof(long)) and nobody cared if the > 64th node is not handled properly. But if the user application > defers the masking to the kernel and provides the number of valid bits > in maxnodes, there is always the last node missing. > However this also affect the special case with maxnodes=0, the manpage > reads that mbind(ptr, len, MPOL_DEFAULT, &some_long, 0, 0); should > reset the policy to the default one, but in fact it returns EINVAL. > This patch just removes the decrease-by-one statement, I hope that > there is no workaround code in the wild that relies on the bogus > behavior.
Actually libnuma and likely most existing users rely on it.
The only way to change it would be to add new system calls.
-Andi
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