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Stack Comsumption Problem Caused By the mark_beginning_as_normal Function Making Recursive Calls to Itself #414

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wcventure opened this issue Jan 9, 2019 · 3 comments
Open

Stack Comsumption Problem Caused By the mark_beginning_as_normal Function Making Recursive Calls to Itself #414

wcventure opened this issue Jan 9, 2019 · 3 comments

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@wcventure
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wcventure commented Jan 9, 2019 •
edited
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Hi there,

An issue was discovered in function mark_beginning_as_normal in nfa.c, as distributed in flex 2.6.4. There is a stack exhaustion problem caused by the in mark_beginning_as_normal function making recursive calls to itself in certain scenarios involving lots of '*' characters.

Here is the POC file. Please use the “./flex $POC” to reproduce the bug.
POC.zip

Command：“./flex $POC”

The ASAN dumps the stack trace as follows:

AddressSanitizer:DEADLYSIGNAL
=================================================================
==30349==ERROR: AddressSanitizer: stack-overflow on address 0x7fffacc27ff8 (pc 0x00000056c257 bp 0x7fffacc28000 sp 0x7fffacc27f80 T0)
    #0 0x56c256 in mark_beginning_as_normal /flex/src/nfa.c:337
    #1 0x56c5e7 in mark_beginning_as_normal /flex/src/nfa.c:348:5
    #2 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #3 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #4 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #5 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #6 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #7 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #8 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #9 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #10 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #11 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #12 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #13 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #14 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #15 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #16 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #17 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #18 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #19 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #20 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #21 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #22 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #23 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #24 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #25 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #26 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #27 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #28 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #29 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #30 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #31 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #32 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #33 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #34 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #35 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #36 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #37 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #38 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #39 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #40 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #41 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #42 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #43 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #44 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #45 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #46 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #47 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #48 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #49 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #50 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #51 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #52 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #53 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #54 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #55 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #56 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #57 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #58 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #59 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #60 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #61 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #62 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #63 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #64 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #65 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #66 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #67 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #68 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #69 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #70 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #71 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #72 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #73 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #74 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #75 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #76 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #77 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #78 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #79 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #80 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #81 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #82 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #83 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #84 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #85 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #86 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #87 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #88 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #89 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #90 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #91 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #92 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #93 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #94 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #95 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #96 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #97 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #98 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #99 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #100 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #101 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #102 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #103 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #104 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #105 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #106 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #107 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #108 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #109 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #110 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #111 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #112 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #113 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #114 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #115 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #116 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #117 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #118 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #119 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #120 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #121 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #122 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #123 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #124 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #125 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #126 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #127 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #128 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #129 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #130 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #131 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #132 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #133 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #134 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #135 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #136 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #137 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #138 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #139 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #140 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #141 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #142 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #143 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #144 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #145 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #146 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #147 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #148 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #149 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #150 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #151 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #152 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #153 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #154 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #155 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #156 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #157 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #158 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #159 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #160 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #161 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #162 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #163 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #164 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #165 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #166 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #167 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #168 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #169 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #170 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #171 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #172 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #173 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #174 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #175 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #176 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #177 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #178 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #179 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #180 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #181 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #182 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #183 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #184 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #185 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #186 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #187 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #188 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #189 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #190 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #191 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #192 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #193 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
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    #195 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
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    #219 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #220 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #221 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
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    #233 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #234 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #235 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #236 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #237 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #238 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #239 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #240 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #241 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #242 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #243 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #244 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #245 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #246 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #247 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #248 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5
    #249 0x56c74f in mark_beginning_as_normal /flex/src/nfa.c:351:5

SUMMARY: AddressSanitizer: stack-overflow /flex/src/nfa.c:337 in mark_beginning_as_normal
==30349==ABORTING
@wcventure
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We can directly look at the snippet code of nfa.c to see if it is possible to have infinite recursion. Intuitively, in some cases, function mark_beginning_as_normal shows the behavior of recursive calls.

void    mark_beginning_as_normal (int mach) {
	switch (state_type[mach]) {
	case STATE_NORMAL:
		/* Oh, we've already visited here. */
		return;

	case STATE_TRAILING_CONTEXT:
		state_type[mach] = STATE_NORMAL;

		if (transchar[mach] == SYM_EPSILON) {
			if (trans1[mach] != NO_TRANSITION)
				mark_beginning_as_normal (trans1[mach]);

			if (trans2[mach] != NO_TRANSITION)
				mark_beginning_as_normal (trans2[mach]);
		}
		break;
	
	}
}

This is simply running out of stack space. You can make the number of recursions go up by 11,000 or so by dynamically allocating variables instead of using stack space, but at the end of the day, you can work around this (for this test case) by doing:

ulimit -s 4096

Of course, a much larger (deeper) YAML file will still make it crash. You can thus, make it happen far faster by doing:

ulimit -s 256

The crash does not seem to happen due to any buffer overflows or memory corruption; it's simply the kernel saying "you're out of stack space, please die". One simple way to avoid the crash itself is to do a depth-check of the tree and compare it to some value related to the stack size returned and produce an error if the values are way out of whack.

A more complicated solution would involve removing recursion, which looks like it would not be a trivial fix.

@andrew-d andrew-d mentioned this issue Feb 16, 2019
Closed
1 task
@niontive niontive mentioned this issue Oct 30, 2020
Merged
10 tasks
woodsts pushed a commit to woodsts/buildroot that referenced this issue Apr 24, 2021
@rc-matthew-l-weber @yann-morin-1998
package/flex: ignore CVE-2019-6293
120d124 
https://security-tracker.debian.org/tracker/CVE-2019-6293

NixOS/nixpkgs#55386 (comment)
 "But this bug does not cause stack overflows in the generated code.
 The function and file referred to in the bug (mark_beginning_as_normal
 in nfa.c) are part of the flex code generator, not part of the
 generated code. If flex crashes before generating any code, that
 can hardly be a vulnerability. If flex does not crash, the generated
 code is fine (or perhaps subject to other unreported bugs, who knows,
 but the NFA has been generated correctly)."

Upstream has chosen to not provide a fix
 westes/flex#414

Signed-off-by: Matthew Weber <[email protected]>
[[email protected]: use actual upstream URL]
Signed-off-by: Yann E. MORIN <[email protected]>
buildroot-auto-update pushed a commit to buildroot/buildroot that referenced this issue Apr 26, 2021
@rc-matthew-l-weber @jacmet
package/flex: ignore CVE-2019-6293
9d8f5a4 
https://security-tracker.debian.org/tracker/CVE-2019-6293

NixOS/nixpkgs#55386 (comment)
 "But this bug does not cause stack overflows in the generated code.
 The function and file referred to in the bug (mark_beginning_as_normal
 in nfa.c) are part of the flex code generator, not part of the
 generated code. If flex crashes before generating any code, that
 can hardly be a vulnerability. If flex does not crash, the generated
 code is fine (or perhaps subject to other unreported bugs, who knows,
 but the NFA has been generated correctly)."

Upstream has chosen to not provide a fix
 westes/flex#414

Signed-off-by: Matthew Weber <[email protected]>
[[email protected]: use actual upstream URL]
Signed-off-by: Yann E. MORIN <[email protected]>
(cherry picked from commit 120d124)
Signed-off-by: Peter Korsgaard <[email protected]>
halstead pushed a commit to openembedded/openembedded-core that referenced this issue Sep 7, 2021
@rpurdie
flex: Add CVE-2019-6293 to exclusions for checks
0cae5d7 
CVE is effectively disputed - yes there is stack exhaustion but no bug and it
is building the parser, not running it, effectively similar to a compiler ICE.
Upstream no plans to address and there is no security issue.

westes/flex#414

Signed-off-by: Richard Purdie <[email protected]>
kraj pushed a commit to YoeDistro/poky-old that referenced this issue Sep 7, 2021
@rpurdie
flex: Add CVE-2019-6293 to exclusions for checks
eec3f74 
CVE is effectively disputed - yes there is stack exhaustion but no bug and it
is building the parser, not running it, effectively similar to a compiler ICE.
Upstream no plans to address and there is no security issue.

westes/flex#414

(From OE-Core rev: 0cae5d7a24bedf6784781b62cbb3795a44bab4d1)

Signed-off-by: Richard Purdie <[email protected]>
kraj pushed a commit to YoeDistro/poky-old that referenced this issue Sep 7, 2021
@rpurdie
flex: Add CVE-2019-6293 to exclusions for checks
0692bd7 
CVE is effectively disputed - yes there is stack exhaustion but no bug and it
is building the parser, not running it, effectively similar to a compiler ICE.
Upstream no plans to address and there is no security issue.

westes/flex#414

(From OE-Core rev: 0cae5d7a24bedf6784781b62cbb3795a44bab4d1)

Signed-off-by: Richard Purdie <[email protected]>
seambot pushed a commit to seamapi/poky that referenced this issue Sep 7, 2021
@rpurdie
flex: Add CVE-2019-6293 to exclusions for checks
8632de2 
CVE is effectively disputed - yes there is stack exhaustion but no bug and it
is building the parser, not running it, effectively similar to a compiler ICE.
Upstream no plans to address and there is no security issue.

westes/flex#414

(From OE-Core rev: 0cae5d7a24bedf6784781b62cbb3795a44bab4d1)

Signed-off-by: Richard Purdie <[email protected]>
halstead pushed a commit to openembedded/openembedded-core that referenced this issue Sep 14, 2021
@rpurdie @sakoman
flex: Add CVE-2019-6293 to exclusions for checks
b939b00 
CVE is effectively disputed - yes there is stack exhaustion but no bug and it
is building the parser, not running it, effectively similar to a compiler ICE.
Upstream no plans to address and there is no security issue.

westes/flex#414

Signed-off-by: Richard Purdie <[email protected]>
(cherry picked from commit 0cae5d7)
Signed-off-by: Steve Sakoman <[email protected]>
seambot pushed a commit to seamapi/poky that referenced this issue Sep 14, 2021
@rpurdie
flex: Add CVE-2019-6293 to exclusions for checks
6aa55dd 
CVE is effectively disputed - yes there is stack exhaustion but no bug and it
is building the parser, not running it, effectively similar to a compiler ICE.
Upstream no plans to address and there is no security issue.

westes/flex#414

(From OE-Core rev: b939b005b06be58a276d565f755ee2d8f3e5dfc1)

Signed-off-by: Richard Purdie <[email protected]>
(cherry picked from commit 0cae5d7a24bedf6784781b62cbb3795a44bab4d1)
Signed-off-by: Steve Sakoman <[email protected]>
Signed-off-by: Richard Purdie <[email protected]>
jpuhlman pushed a commit to MontaVista-OpenSourceTechnology/poky that referenced this issue Sep 16, 2021
@rpurdie @jpuhlman
flex: Add CVE-2019-6293 to exclusions for checks
504c7fa 
Source: poky
MR: 112421
Type: Integration
Disposition: Merged from poky
ChangeID: 6aa55dd279b14b34f334b8d70f7046720fc6764d
Description:

CVE is effectively disputed - yes there is stack exhaustion but no bug and it
is building the parser, not running it, effectively similar to a compiler ICE.
Upstream no plans to address and there is no security issue.

westes/flex#414

(From OE-Core rev: b939b005b06be58a276d565f755ee2d8f3e5dfc1)

Signed-off-by: Richard Purdie <[email protected]>
(cherry picked from commit 0cae5d7a24bedf6784781b62cbb3795a44bab4d1)
Signed-off-by: Steve Sakoman <[email protected]>
Signed-off-by: Richard Purdie <[email protected]>
Signed-off-by: Jeremy A. Puhlman <[email protected]>
halstead pushed a commit to openembedded/openembedded-core that referenced this issue Sep 17, 2021
@rpurdie @anujm1
flex: Add CVE-2019-6293 to exclusions for checks
e2de2e5 
CVE is effectively disputed - yes there is stack exhaustion but no bug and it
is building the parser, not running it, effectively similar to a compiler ICE.
Upstream no plans to address and there is no security issue.

westes/flex#414

Signed-off-by: Richard Purdie <[email protected]>
(cherry picked from commit 0cae5d7)
Signed-off-by: Anuj Mittal <[email protected]>
seambot pushed a commit to seamapi/poky that referenced this issue Sep 17, 2021
@rpurdie
flex: Add CVE-2019-6293 to exclusions for checks
374cefd 
CVE is effectively disputed - yes there is stack exhaustion but no bug and it
is building the parser, not running it, effectively similar to a compiler ICE.
Upstream no plans to address and there is no security issue.

westes/flex#414

(From OE-Core rev: e2de2e5e977d84dab6cb1461800d4c29436da5c9)

Signed-off-by: Richard Purdie <[email protected]>
(cherry picked from commit 0cae5d7a24bedf6784781b62cbb3795a44bab4d1)
Signed-off-by: Anuj Mittal <[email protected]>
Signed-off-by: Richard Purdie <[email protected]>
@xiaoge1001
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Does anyone care about this?

@Mightyjo
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Mightyjo commented Jun 13, 2023 •
edited
Loading

Short answer: nfa.c is working as intended.

Looks like the failing input comes from a fuzzer. It consists of around 16KB of *s in a row, plus some other junk.

The crash occurs in flex itself, not the scanner produced by flex. The protection against exploit is to not run flex setuid. This is already the default.

I'm not very concerned that we see stack exhaustion when someone feeds exceptionally long garbage input to flex. Detecting that before processing would require solving the halting problem so we just have to begin. If there's a cleaner way to fail, I'm glad to hear it of course. Also, if there's a smaller, more realistic POC that would be something to consider.

daregit pushed a commit to daregit/yocto-combined that referenced this issue May 22, 2024
@rpurdie
src/poky:flex: Add CVE-2019-6293 to exclusions for checks
62239c4 
CVE is effectively disputed - yes there is stack exhaustion but no bug and it
is building the parser, not running it, effectively similar to a compiler ICE.
Upstream no plans to address and there is no security issue.

westes/flex#414

(From OE-Core rev: 0cae5d7a24bedf6784781b62cbb3795a44bab4d1)

Signed-off-by: Richard Purdie <[email protected]>
daregit pushed a commit to daregit/yocto-combined that referenced this issue May 22, 2024
@rpurdie
src/poky:flex: Add CVE-2019-6293 to exclusions for checks
1d854aa 
CVE is effectively disputed - yes there is stack exhaustion but no bug and it
is building the parser, not running it, effectively similar to a compiler ICE.
Upstream no plans to address and there is no security issue.

westes/flex#414

(From OE-Core rev: 0cae5d7a24bedf6784781b62cbb3795a44bab4d1)

Signed-off-by: Richard Purdie <[email protected]>
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@Mightyjo @wcventure @xiaoge1001