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The old code used l_init_called as an indicator for whether TLS initialization was complete. However, it is possible that TLS for an object is initialized, written to, and then dlopen for this object is called again, and l_init_called is not true at this point. Previously, this resulted in TLS being initialized twice, discarding any interim writes (technically introducing a use-after-free bug even). This commit introduces an explicit per-object flag, l_tls_in_slotinfo. It indicates whether _dl_add_to_slotinfo has been called for this object. This flag is used to avoid double-initialization of TLS. In update_tls_slotinfo, the first_static_tls micro-optimization is removed because preserving the initalization flag for subsequent use by the second loop for static TLS is a bit complicated, and another per-object flag does not seem to be worth it. Furthermore, the l_init_called flag is dropped from the second loop (for static TLS initialization) because l_need_tls_init on its own prevents double-initialization. The remaining l_init_called usage in resize_scopes and update_scopes is just an optimization due to the use of scope_has_map, so it is not changed in this commit. The isupper check ensures that libc.so.6 is TLS is not reverted. Such a revert happens if l_need_tls_init is not cleared in _dl_allocate_tls_init for the main_thread case, now that l_init_called is not checked anymore in update_tls_slotinfo in elf/dl-open.c. Reported-by: Jonathon Anderson <janderson@rice.edu> Reviewed-by: Carlos O'Donell <carlos@redhat.com>
103 lines
3.1 KiB
C
103 lines
3.1 KiB
C
/* Test that dlopen preserves already accessed TLS (bug 31717), module 3.
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Copyright (C) 2024 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <dlfcn.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <unistd.h>
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/* Used to verify from the main program that the test ran. */
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bool tlsreinitmod3_tested;
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/* This TLS variable must not revert back to the initial state after
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dlopen. */
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static __thread int tlsreinitmod3_state = 1;
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/* Set from the ELF constructor during dlopen. */
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static bool tlsreinitmod3_constructed;
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/* Second half of test, behind a compiler barrier. The compiler
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barrier is necessary to prevent carrying over TLS address
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information from call_tlsreinitmod3 to call_tlsreinitmod3_tail. */
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void call_tlsreinitmod3_tail (void *self) __attribute__ ((weak));
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/* Called from tst-dlopen-tlsreinitmod2.so. */
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void
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call_tlsreinitmod3 (void)
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{
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printf ("info: call_tlsreinitmod3 invoked (state=%d)\n",
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tlsreinitmod3_state);
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if (tlsreinitmod3_constructed)
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{
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puts ("error: call_tlsreinitmod3 called after ELF constructor");
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fflush (stdout);
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/* Cannot rely on test harness due to dynamic linking. */
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_exit (1);
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}
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tlsreinitmod3_state = 2;
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/* Self-dlopen. This will run the ELF constructor. */
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void *self = dlopen ("tst-dlopen-tlsreinitmod3.so", RTLD_NOW);
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if (self == NULL)
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{
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printf ("error: dlopen: %s\n", dlerror ());
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fflush (stdout);
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/* Cannot rely on test harness due to dynamic linking. */
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_exit (1);
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}
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call_tlsreinitmod3_tail (self);
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}
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void
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call_tlsreinitmod3_tail (void *self)
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{
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printf ("info: dlopen returned in tlsreinitmod3 (state=%d)\n",
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tlsreinitmod3_state);
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if (!tlsreinitmod3_constructed)
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{
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puts ("error: dlopen did not call tlsreinitmod3 ELF constructor");
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fflush (stdout);
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/* Cannot rely on test harness due to dynamic linking. */
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_exit (1);
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}
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if (tlsreinitmod3_state != 2)
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{
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puts ("error: TLS state reverted in tlsreinitmod3");
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fflush (stdout);
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/* Cannot rely on test harness due to dynamic linking. */
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_exit (1);
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}
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dlclose (self);
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/* Signal test completion to the main program. */
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tlsreinitmod3_tested = true;
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}
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static void __attribute__ ((constructor))
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tlsreinitmod3_init (void)
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{
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puts ("info: constructor of tst-dlopen-tlsreinitmod3.so invoked");
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tlsreinitmod3_constructed = true;
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}
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