mpm-ac: fix integer overflow on allocation #2546
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The size of a memory buffer to be allocated was kept in a signed int instead of a size_t, leading to an overflow when large lists of long and diverse patterns cause the amount of AC states to blow up (>2GB). Fixes Redmine issues OISF#1827 and OISF#1843. Signed-off-by: Sascha Steinbiss <sascha@steinbiss.name>
inliniac
reviewed
Feb 8, 2017
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| /* reallocate space in the goto table to include a new state */ | ||
| size = cnt * ctx->single_state_size; | ||
| size = SCACCheckSafeSizetMult((size_t) cnt, (size_t) ctx->single_state_size); | ||
| ptmp = SCRealloc(ctx->goto_table, size); |
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Interestingly, scan-build-3.9 now warns that size could be 0:
util-mpm-ac.c:160:12: warning: Call to 'realloc' has an allocation size of 0 bytes
ptmp = SCRealloc(ctx->goto_table, size);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./util-mem.h:193:14: note: expanded from macro 'SCRealloc'
ptrmem = realloc((x), (a)); \
^~~~~~~~~~~~~~~~~
1 warning generated.
I guess a simple size check would fix it. It is out goal to get to 0 issues in scan-build (and other checkers), even if they are sometimes far-fetched or even wrong. So we'll need a fix.
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Sure, I'll look into it. I can totally understand the goal of static checker cleanness -- we have also used scan-build (as a successor of splint) in previous projects.
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The size of a memory buffer to be reallocated during state creation in the Aho-Corasick implementation was kept in a signed
intinstead of asize_t, leading to an overflow when large lists of long and diverse patterns cause the amount of AC states to blow up (>2GB). This case can be triggered for reproduction using a script like https://gist.github.com/satta/e47f7a6f0e44c9898804121e4d8c5f2e.Addresses Redmine issues #1827 (https://redmine.openinfosecfoundation.org/issues/1827) and #1843 (https://redmine.openinfosecfoundation.org/issues/1843).
This PR adds the following functionality:
SCACCheckSafeSizetMult()to check whether asize_tmultiplication overflows,exit()ing in this case.sizevariable inSCACReallocState()tosize_t.I ran the Dockerized prscript, builds completed successfully: