| Summary: | ld.so should not require that a versioned symbol is always implemented in the same library | ||
|---|---|---|---|
| Product: | glibc | Reporter: | Florian Weimer <fweimer> |
| Component: | dynamic-link | Assignee: | Florian Weimer <fweimer> |
| Status: | RESOLVED FIXED | ||
| Severity: | enhancement | Flags: | fweimer:
security-
|
| Priority: | P2 | ||
| Version: | 2.30 | ||
| Target Milestone: | 2.30 | ||
| See Also: | https://bugzilla.redhat.com/show_bug.cgi?id=1748194 | ||
| Host: | Target: | ||
| Build: | Last reconfirmed: | ||
| Bug Depends on: | |||
| Bug Blocks: | 20188, 20220, 24959 | ||
|
Description
Florian Weimer
2019-06-27 12:05:10 UTC
The master branch has been updated by Florian Weimer <fw@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=f0b2132b35248c1f4a80f62a2c38cddcc802aa8c commit f0b2132b35248c1f4a80f62a2c38cddcc802aa8c Author: Florian Weimer <fweimer@redhat.com> Date: Fri Jun 28 10:12:50 2019 +0200 ld.so: Support moving versioned symbols between sonames [BZ #24741] This change should be fully backwards-compatible because the old code aborted the load if a soname mismatch was encountered (instead of searching further for a matching symbol). This means that no different symbols are found. The soname check was explicitly disabled for the skip_map != NULL case. However, this only happens with dl(v)sym and RTLD_NEXT, and those lookups do not come with a verneed entry that could be used for the check. The error check was already explicitly disabled for the skip_map != NULL case, that is, when dl(v)sym was called with RTLD_NEXT. But _dl_vsym always sets filename in the struct r_found_version argument to NULL, so the check was not active anyway. This means that symbol lookup results for the skip_map != NULL case do not change, either. Fixed in glibc 2.30. The master branch has been updated by Florian Weimer <fw@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=41d6f74e6cb6a92ab428c11ee1e408b2a16aa1b0 commit 41d6f74e6cb6a92ab428c11ee1e408b2a16aa1b0 Author: Florian Weimer <fweimer@redhat.com> Date: Tue Jul 2 15:12:20 2019 +0200 nptl: Remove vfork IFUNC-based forwarder from libpthread [BZ #20188] With commit f0b2132b35248c1f4a80f62a2c38cddcc802aa8c ("ld.so: Support moving versioned symbols between sonames [BZ #24741]"), the dynamic linker will find the definition of vfork in libc and binds a vfork reference to that symbol, even if the soname in the version reference says that the symbol should be located in libpthread. As a result, the forwarder (whether it's IFUNC-based or a duplicate of the libc implementation) is no longer necessary. On older architectures, a placeholder symbol is required, to make sure that the GLIBC_2.1.2 symbol version does not go away, or is turned in to a weak symbol definition by the link editor. (The symbol version needs to preserved so that the symbol coverage check in elf/dl-version.c does not fail for old binaries.) mips32 is an outlier: It defined __vfork@@GLIBC_2.2, but the baseline is GLIBC_2.0. Since there are other @@GLIBC_2.2 symbols, the placeholder symbol is not needed there. The master branch has been updated by Florian Weimer <fw@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=3a0ecccb599a6b1ad4b149dc569c0080e92d057b commit 3a0ecccb599a6b1ad4b149dc569c0080e92d057b Author: Florian Weimer <fweimer@redhat.com> Date: Sat Feb 8 19:58:43 2020 +0100 ld.so: Do not export free/calloc/malloc/realloc functions [BZ #25486] Exporting functions and relying on symbol interposition from libc.so makes the choice of implementation dependent on DT_NEEDED order, which is not what some compiler drivers expect. This commit replaces one magic mechanism (symbol interposition) with another one (preprocessor-/compiler-based redirection). This makes the hand-over from the minimal malloc to the full malloc more explicit. Removing the ABI symbols is backwards-compatible because libc.so is always in scope, and the dynamic loader will find the malloc-related symbols there since commit f0b2132b35248c1f4a80f62a2c38cddcc802aa8c ("ld.so: Support moving versioned symbols between sonames [BZ #24741]"). Reviewed-by: Carlos O'Donell <carlos@redhat.com> |