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* [Bug dynamic-link/31168] New: ld.so startup segfaults if constructor does dlopen with RTLD_GLOBAL
@ 2023-12-14 22:35 srk31 at srcf dot ucam.org
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From: srk31 at srcf dot ucam.org @ 2023-12-14 22:35 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=31168
Bug ID: 31168
Summary: ld.so startup segfaults if constructor does dlopen
with RTLD_GLOBAL
Product: glibc
Version: 2.35
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: dynamic-link
Assignee: unassigned at sourceware dot org
Reporter: srk31 at srcf dot ucam.org
Target Milestone: ---
Created attachment 15260
--> https://sourceware.org/bugzilla/attachment.cgi?id=15260&action=edit
small reproducer
The ld.so of glibc 2.36 (and likely later but I haven't tested) may crash
during _dl_init of the main executable, if an early constructor does a dlopen
with RTLD_GLOBAL.
The problem seems to be that `add_to_global_update()` adds to
`main_map->l_searchlist.r_nlist` but `main_map->l_initfini` is not resized to
match. This is a problem since `r_nlist` is used to bound the call_init loop in
dl-init.c, which ranges over `l_initfini`:
135 i = main_map->l_searchlist.r_nlist;
136 while (i-- > 0)
137 call_init (main_map->l_initfini[i], argc, argv, env);
... meaning the loop will run off the end of the `l_initfini` list, calling
`call_init` passing the NULL terminator value instead of a link map.
See attached test case... this is doing dlopen during the constructor of an
initfirst preloaded object. I'm not sure whether it can be reproduced without
initfirst and/or preloading... this combination closely models my use case,
which was working fine until at least 2.28.
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2023-12-14 22:35 [Bug dynamic-link/31168] New: ld.so startup segfaults if constructor does dlopen with RTLD_GLOBAL srk31 at srcf dot ucam.org
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