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* [glibc/nsz/bug23293] elf: Remove fallback to the start of DT_STRTAB for dladdr
@ 2022-05-04 6:02 Szabolcs Nagy
0 siblings, 0 replies; only message in thread
From: Szabolcs Nagy @ 2022-05-04 6:02 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=8e28aa3a51bf0ef3683f2aed4b5b448744897b66
commit 8e28aa3a51bf0ef3683f2aed4b5b448744897b66
Author: Fangrui Song <maskray@google.com>
Date: Mon May 2 09:06:39 2022 -0700
elf: Remove fallback to the start of DT_STRTAB for dladdr
When neither DT_HASH nor DT_GNU_HASH is present, the code scans
[DT_SYMTAB, DT_STRTAB). However, there is no guarantee that .dynstr
immediately follows .dynsym (e.g. lld typically places .gnu.version
after .dynsym).
In the absence of a hash table, symbol lookup will always fail
(map->l_nbuckets == 0 in dl-lookup.c) as if the object has no symbol, so
it seems fair for dladdr to do the same.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Diff:
---
elf/dl-addr.c | 16 +++++-----------
1 file changed, 5 insertions(+), 11 deletions(-)
diff --git a/elf/dl-addr.c b/elf/dl-addr.c
index e3c5598e1a..c4278075ef 100644
--- a/elf/dl-addr.c
+++ b/elf/dl-addr.c
@@ -71,18 +71,10 @@ determine_info (const ElfW(Addr) addr, struct link_map *match, Dl_info *info,
}
}
}
- else
+ else if (match->l_info[DT_HASH] != NULL)
{
- const ElfW(Sym) *symtabend;
- if (match->l_info[DT_HASH] != NULL)
- symtabend = (symtab
- + ((Elf_Symndx *) D_PTR (match, l_info[DT_HASH]))[1]);
- else
- /* There is no direct way to determine the number of symbols in the
- dynamic symbol table and no hash table is present. The ELF
- binary is ill-formed but what shall we do? Use the beginning of
- the string table which generally follows the symbol table. */
- symtabend = (const ElfW(Sym) *) strtab;
+ const ElfW (Sym) *symtabend
+ = (symtab + ((Elf_Symndx *) D_PTR (match, l_info[DT_HASH]))[1]);
for (; (void *) symtab < (void *) symtabend; ++symtab)
if ((ELFW(ST_BIND) (symtab->st_info) == STB_GLOBAL
@@ -96,6 +88,8 @@ determine_info (const ElfW(Addr) addr, struct link_map *match, Dl_info *info,
&& symtab->st_name < strtabsize)
matchsym = (ElfW(Sym) *) symtab;
}
+ /* In the absence of a hash table, treat the object as if it has no symbol.
+ */
if (mapp)
*mapp = match;
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2022-05-04 6:02 [glibc/nsz/bug23293] elf: Remove fallback to the start of DT_STRTAB for dladdr Szabolcs Nagy
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