Messages in this thread | | | Date | Wed, 17 Nov 2021 19:00:39 -0500 | From | Steven Rostedt <> | Subject | Re: [GIT PULL] tracing: Fix double free bug |
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On Wed, 17 Nov 2021 15:38:59 -0800 Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Wed, Nov 17, 2021 at 3:19 PM Steven Rostedt <rostedt@goodmis.org> wrote: > > > > On error, the operands and the histogram expression are destroyed, > > but since the destruction is recursive, do not destroy the operands > > if they already belong to the expression that is about to be destroyed. > > Honestly, this seems horribly ugly.
I guess we have a difference in opinion to what is ugly, as the v1 version of Kalesh's patch was closer to yours, and I hated the complexity of having to know when to to call what. Because the logic is not that simple.
See https://lore.kernel.org/all/20211117021223.2137117-1-kaleshsingh@google.com/
> > The problem seems to be that the "goto error" cases are simply just wrong. > > Why isn't the fix to make the error cases be the right ones, instead > of having one odd error case that then has to do some magic things to > not free the wrong things? > > The patch ends up a bit bigger, mainly because I renamed the different > "free" cases, and because I made the non-freeing ones just return the > error directly.
I agree with the first part of your patch, which was not the reason for being the cause of the bug.
> > Something like this (UNTESTED!) patch, IOW?
But the part after the expr is allocated gets a bit more tricky, and that is why I requested that logic, namely due to the "combine_consts" case. But as the expr->operand[]s are NULL'd and the operand*s are destroyed, I guess it's still fine with just freeing the expr if we add an error case there.
Kalesh, care to spin a v3 implementing Linus's solution?
-- Steve
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