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Date: Sat, 28 Aug 2010 09:15:16 -0400 From: Bob Copeland <me@...copeland.com> To: Matthew Wilcox <matthew@....cx> Cc: Valerie Aurora <vaurora@...hat.com>, Alexander Viro <viro@...iv.linux.org.uk>, Karel Zak <kzak@...hat.com>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] VFS: Sanity check mount flags passed to change_mnt_propagation() On Sat, Aug 28, 2010 at 04:57:07AM -0600, Matthew Wilcox wrote: > > Didn't read surrounding code, but is that supposed to be '||'? > > > > Otherwise the case where only a single non-propagation flag is > > set no longer returns 0... > > Val's original code returned 0 as failure. So a single non-propagation > flag set shouldn't return 0. Not to belabor the point -- but her original code did return zero in that case (2nd assertion fails): #include <linux/fs.h> #include <stdio.h> #include <assert.h> #define hweight32 dumb_hweight32 int dumb_hweight32(int a) { int i; int weight = 0; for (i=0; i < 32; i++) weight += !!(a & (1 << i)); return weight; } static int flags_to_propagation_type(int flags) { int type = flags & ~MS_REC; /* Fail if any non-propagation flags are set */ if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) return 0; /* Only one propagation flag should be set */ if (((type & (MS_SHARED)) && (type & ~MS_SHARED)) || ((type & (MS_PRIVATE)) && (type & ~MS_PRIVATE)) || ((type & (MS_SLAVE)) && (type & ~MS_SLAVE)) || ((type & (MS_UNBINDABLE)) && (type & ~MS_UNBINDABLE))) return 0; return type; } static int flags_to_propagation_type_2(int flags) { int type = flags & ~MS_REC; /* Only one propagation flag should be set, and no others */ if (hweight32(type) != 1 && (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))) return 0; return type; } int main(int argc, char *argv[]) { int mytype = MS_RDONLY; assert(flags_to_propagation_type(mytype) == 0); assert(flags_to_propagation_type_2(mytype) == 0); } -- Bob Copeland %% www.bobcopeland.com -- 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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