In perl.git, the branch smoke-me/khw-134329 has been created
<https://perl5.git.perl.org/perl.git/commitdiff/84072a0538b77a4779496395ccb47a158b882329?hp=0000000000000000000000000000000000000000>
at 84072a0538b77a4779496395ccb47a158b882329 (commit)
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commit 84072a0538b77a4779496395ccb47a158b882329
Author: Karl Williamson <[email protected]>
Date: Fri Aug 23 12:40:24 2019 -0600
PATCH: [perl #134329] Use after free in regcomp.c
A compiled regex is composed of nodes, forming a linked list, with
normally a maximum of 16 bits used to specify the offset of the next
link. For patterns that require more space than this, the nodes that
jump around are replaced with ones that have wider offsets. Most nodes
are unaffected, as they just contain the offset of the next node, and
that number is always small. The jump nodes are the ones affected.
When compiling a pattern, the 16 bit mechanism is used, until it
overflows, at which point the pattern is recompiled with the long jumps
instead.
When I rewrote the compiler last year to make it generally one pass, I
noticed a lot of the cases where a node was added didn't check if the
result overflowed (the function that does this returns FALSE in that
case). I presumed the prior authors knew better, and did not change
things, except to put in a bogus value in the link (offset) field that
should cause a crash if it were used. That's what's happening in this
ticket.
But seeing this example, it's clear that the return value should be
checked every time, because you can reach the limit at any time. This
commit changes to do that, and to require the function's return value to
not be ignored, to guard against future changes.
My guess is that the reason it generally worked when there were multiple
passes is that the first pass didn't do anything except count space, and
that at some point before the end of the pass the return value did get
checked, so by the time the nodes were allocated for real, it knew
enough to use the long jumps.
commit b5cb7d3dbe3e2e57eb208587698cefb806cc4801
Author: Karl Williamson <[email protected]>
Date: Mon Nov 26 20:16:09 2018 -0700
XXX need to do process; figure name Configure Fix alignment needed probe
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