[Bug regex/18037] New: infinite recursion (stack overflow) in regexec.c (sift_states_bkref->sift_states_backward->update_cur_sifted_state)

["konstantin.s.serebryany at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=18037

            Bug ID: 18037
           Summary: infinite recursion (stack overflow) in regexec.c
                    (sift_states_bkref->sift_states_backward->update_cur_s
                    ifted_state)
           Product: glibc
           Version: 2.21
            Status: NEW
          Severity: normal
          Priority: P2
         Component: regex
          Assignee: unassigned at sourceware dot org
          Reporter: konstantin.s.serebryany at gmail dot com
                CC: drepper.fsp at gmail dot com

#include <regex.h>                                                              
int main() {                                                                    
  regex_t r;                                                                    
  if (!regcomp(&r, "()\\1++", REG_EXTENDED))
    regexec(&r, "foo.*bar", 0, 0, 0);                                           
}

gcc -g re1.c && ./a.out


#0  0x00007ffff7aeb1ec in re_acquire_state (err=err@entry=0x7fffff7ff0e0,
dfa=dfa@entry=0x602120, nodes=nodes@entry=0x7fffff7ff190) at
regex_internal.c:1480
#1  0x00007ffff7aed91d in add_epsilon_src_nodes (candidates=0x602b38,
dest_nodes=0x7fffff7ff190, dfa=0x602120) at regexec.c:1825
#2  update_cur_sifted_state (mctx=mctx@entry=0x7fffffffdb50,
sctx=sctx@entry=0x7fffff7ff290, str_idx=str_idx@entry=0,
dest_nodes=dest_nodes@entry=0x7fffff7ff190) at regexec.c:1789
#3  0x00007ffff7aee428 in sift_states_backward (mctx=mctx@entry=0x7fffffffdb50,
sctx=sctx@entry=0x7fffff7ff290) at regexec.c:1614
#4  0x00007ffff7aedd69 in sift_states_bkref (candidates=0x602b38, str_idx=0,
sctx=<optimized out>, mctx=0x7fffffffdb50) at regexec.c:2199
#5  update_cur_sifted_state (mctx=mctx@entry=0x7fffffffdb50,
sctx=sctx@entry=0x7fffff7ff440, str_idx=str_idx@entry=0,
dest_nodes=dest_nodes@entry=0x7fffff7ff340) at regexec.c:1810
#6  0x00007ffff7aee428 in sift_states_backward (mctx=mctx@entry=0x7fffffffdb50,
sctx=sctx@entry=0x7fffff7ff440) at regexec.c:1614
#7  0x00007ffff7aedd69 in sift_states_bkref (candidates=0x602b38, str_idx=0,
sctx=<optimized out>, mctx=0x7fffffffdb50) at regexec.c:2199

...

Reproduces on 2.19 and trunk. 

I am not sure if this bug is too interesting by itself, 
but my fuzzer hits it instantly and does not let me find anything more
exciting. (Same fuzzer as in bug 18032 and bug 18036)

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