When the application creates alternative namespaces with dlmopen, ld.so is loaded as a “fake” object into that namespace and la_objopen is not called, even though la_objclose is called on it later once the namespace is dlclose’d. Due to the limited argument set passed to la_objclose (only the uintptr_t cookie), the auditor is called with a cookie it has never set before and must decipher whether it points to its own structures or the default link_map. There are two ways to look at it. You really aren't "opening" ld.so when it is imported into the new namepsace's link map. So I can understand why la_objopen() isn't being called. However, that being the case, I think that it shouldn't trigger la_objclose() either. Or I can see how importing it into the new namespace is like opening it and we are just forgetting to call la_opbopen() in that case. I think whichever way, the behavior should match.However, I think the most logical solution is to call la_objopen() from the code which imports ld.so into the private namespace. Reproducible: Always Steps to Reproduce: 1. tar xvzf missing-open-for-ldso.tar.gz 2. cd missing-open-for-ldso/ 3. make Actual Results: $ make gcc -o libauditor.so auditor.c -fPIC -shared gcc -o main main.c -ldl gcc -o libother.so libother.c -fPIC -shared Success requires OK (not FAIL) at the end of each line: LD_AUDIT=./libauditor.so ./main la_objopen('./main', lmid: 0), cookie 0x7f36d1172798 now = 2 la_objopen('/lib64/ld-linux-x86-64.so.2', lmid: 0), cookie 0x7f36d1171f68 now = 2 la_objopen('linux-vdso.so.1', lmid: 0), cookie 0x7f36d1172d78 now = 2 la_objopen('/lib64/libc.so.6', lmid: 0), cookie 0x7f36d110cf58 now = 2 Calling dlmopen(libother.so) [1]... la_activity('./libother.so', LA_ACT_ADD), cookie 0x178acb88 now = 1 la_objopen('./libother.so', lmid: 2), cookie 0x178acb88 now = 2 la_objopen('/lib64/libc.so.6', lmid: 2), cookie 0x178ad148 now = 2 Calling dlmopen(libother.so) [2]... la_activity('./libother.so', LA_ACT_ADD), cookie 0x178ae0f8 now = 1 la_objopen('./libother.so', lmid: 3), cookie 0x178ae0f8 now = 2 la_objopen('/lib64/libc.so.6', lmid: 3), cookie 0x178ae6b8 now = 2 Calling dlmopen(libother.so) [3]... la_activity('./libother.so', LA_ACT_ADD), cookie 0x178af668 now = 1 la_objopen('./libother.so', lmid: 4), cookie 0x178af668 now = 2 la_objopen('/lib64/libc.so.6', lmid: 4), cookie 0x178afc28 now = 2 Calling dlclose([1])... la_objclose(0x178acb88)... OK. la_objclose(0x178ad148)... OK. la_objclose('/lib64/ld-linux-x86-64.so.2')... FAIL. (cookie unset) Calling dlclose([2])... la_objclose(0x178ae0f8)... OK. la_objclose(0x178ae6b8)... OK. la_objclose('/lib64/ld-linux-x86-64.so.2')... FAIL. (cookie unset) Calling dlclose([3])... la_objclose(0x178af668)... OK. la_objclose(0x178afc28)... OK. la_objclose('/lib64/ld-linux-x86-64.so.2')... FAIL. (cookie unset) Exiting... la_objclose(0x7f36d1172798)... OK. la_objclose(0x7f36d110cf58)... OK. la_objclose(0x7f36d1171f68)... OK. Expected Results: $ make gcc -o libauditor.so auditor.c -fPIC -shared gcc -o main main.c -ldl gcc -o libother.so libother.c -fPIC -shared Success requires OK (not FAIL) at the end of each line: LD_AUDIT=./libauditor.so ./main la_objopen('./main', lmid: 0), cookie 0x7f36d1172798 now = 2 la_objopen('/lib64/ld-linux-x86-64.so.2', lmid: 0), cookie 0x7f36d1171f68 now = 2 la_objopen('linux-vdso.so.1', lmid: 0), cookie 0x7f36d1172d78 now = 2 la_objopen('/lib64/libc.so.6', lmid: 0), cookie 0x7f36d110cf58 now = 2 Calling dlmopen(libother.so) [1]... la_activity('./libother.so', LA_ACT_ADD), cookie 0x178acb88 now = 1 la_objopen('./libother.so', lmid: 2), cookie 0x178acb88 now = 2 la_objopen('/lib64/libc.so.6', lmid: 2), cookie 0x178ad148 now = 2 Calling dlmopen(libother.so) [2]... la_activity('./libother.so', LA_ACT_ADD), cookie 0x178ae0f8 now = 1 la_objopen('./libother.so', lmid: 3), cookie 0x178ae0f8 now = 2 la_objopen('/lib64/libc.so.6', lmid: 3), cookie 0x178ae6b8 now = 2 Calling dlmopen(libother.so) [3]... la_activity('./libother.so', LA_ACT_ADD), cookie 0x178af668 now = 1 la_objopen('./libother.so', lmid: 4), cookie 0x178af668 now = 2 la_objopen('/lib64/libc.so.6', lmid: 4), cookie 0x178afc28 now = 2 Calling dlclose([1])... la_objclose(0x178acb88)... OK. la_objclose(0x178ad148)... OK. la_objclose(0xSOMEADDRESS)... OK Calling dlclose([2])... la_objclose(0x178ae0f8)... OK. la_objclose(0x178ae6b8)... OK. la_objclose(0xSOMEADDRESS)... OK Calling dlclose([3])... la_objclose(0x178af668)... OK. la_objclose(0x178afc28)... OK. la_objclose(0xSOMEADDRESS)... OK Exiting... la_objclose(0x7f36d1172798)... OK. la_objclose(0x7f36d110cf58)... OK. la_objclose(0x7f36d1171f68)... OK. The point is the cookie used to call la_objclose() is known to the tool because the it was provided to the tool with an la_objopen() call.
Created attachment 2039802 [details] reproducer to run the reproducer simply: tar xvzf missing-open-for-ldso.tar.gz cd missing-open-for-ldso make
Florian posted an upstream series to resolve the issue: https://patchwork.sourceware.org/project/glibc/list/?series=38193 Still under review upstream.
Review had changes-requested for one of the series patches. Ongoing upstream work.
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Upstream commit: commit 8f36b1469677afe37168f9af1b77402d7a70c673 Author: Florian Weimer <fweimer> Date: Fri Aug 9 15:31:18 2024 +0200 elf: Signal la_objopen for the proxy link map in dlmopen (bug 31985) Previously, the ld.so link map was silently added to the namespace. This change produces an auditing event for it. Reviewed-by: Adhemerval Zanella <adhemerval.zanella> This and commits in the vicinity went into glibc-2.40.9000-25.fc42.