Messages in this thread | | | Date | Mon, 6 Mar 2006 23:07:55 +0100 | From | Pavel Machek <> | Subject | Re: 9pfs double kfree |
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On Po 06-03-06 09:34:01, Al Viro wrote: > On Mon, Mar 06, 2006 at 10:40:03AM +0200, Kai Makisara wrote: > > > Legal, but rather bad taste. Init to NULL, possibly assign the value > > > if kmalloc(), then kfree() unconditionally - sure, but that... almost > > > certainly one hell of a lousy cleanup logics somewhere. > > > > > I agree with you. > > > > However, a few months ago it was advocated to let kfree take care of > > testing the pointer against NULL and a load of patches like this: > > That's different - that's _exactly_ the case I've mentioned above. > > Moreover, that's exact match to standard behaviour of free(3): > > C99 7.20.3.2(2): > The free function causes the space pointed to by ptr to be deallocated, that > is, made available for further allocation. If ptr is a null pointer, no action > occurs. Otherwise, if the argument does not match a pointer returned by the > calloc, malloc, or realloc function, or if the space has been deallocated by > a call to free or realloc, the behaviour is undefined. > > IOW, free(NULL) is guaranteed to be no-op while double-free is nasal daemon > country.
Well, double-free of NULL is permitted by text above. 'If ptr is a null pointer, no action occurs.'
OTOH #define kfree(a) { __kfree(a); a = NULL; } actually does the right thing... even with double free. Pavel -- Web maintainer for suspend.sf.net (www.sf.net/projects/suspend) wanted... - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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