105 lines
3.4 KiB
Diff
105 lines
3.4 KiB
Diff
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commit a2e8aa0d9ea648068d8be52dd7b15f1b6a008e23
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Thu Oct 31 19:30:19 2019 +0100
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Block signals during the initial part of dlopen
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Lazy binding in a signal handler that interrupts a dlopen sees
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intermediate dynamic linker state. This has likely been always
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unsafe, but with the new pending NODELETE state, this is clearly
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incorrect. Other threads are excluded via the loader lock, but the
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current thread is not. Blocking signals until right before ELF
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constructors run is the safe thing to do.
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Change-Id: Iad079080ebe7442c13313ba11dc2797953faef35
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diff --git a/elf/dl-open.c b/elf/dl-open.c
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index 79c6e4c8ed1c9dfa..25838b073ac1edaf 100644
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--- a/elf/dl-open.c
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+++ b/elf/dl-open.c
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@@ -34,6 +34,7 @@
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#include <atomic.h>
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#include <libc-internal.h>
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#include <array_length.h>
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+#include <internal-signals.h>
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#include <dl-dst.h>
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#include <dl-prop.h>
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@@ -52,6 +53,10 @@ struct dl_open_args
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/* Namespace ID. */
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Lmid_t nsid;
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+ /* Original signal mask. Used for unblocking signal handlers before
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+ running ELF constructors. */
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+ sigset_t original_signal_mask;
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+
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/* Original value of _ns_global_scope_pending_adds. Set by
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dl_open_worker. Only valid if nsid is a real namespace
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(non-negative). */
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@@ -524,12 +529,16 @@ dl_open_worker (void *a)
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if (new == NULL)
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{
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assert (mode & RTLD_NOLOAD);
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+ __libc_signal_restore_set (&args->original_signal_mask);
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return;
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}
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if (__glibc_unlikely (mode & __RTLD_SPROF))
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- /* This happens only if we load a DSO for 'sprof'. */
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- return;
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+ {
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+ /* This happens only if we load a DSO for 'sprof'. */
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+ __libc_signal_restore_set (&args->original_signal_mask);
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+ return;
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+ }
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/* This object is directly loaded. */
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++new->l_direct_opencount;
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@@ -565,6 +574,7 @@ dl_open_worker (void *a)
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assert (_dl_debug_initialize (0, args->nsid)->r_state == RT_CONSISTENT);
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+ __libc_signal_restore_set (&args->original_signal_mask);
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return;
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}
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@@ -745,6 +755,10 @@ dl_open_worker (void *a)
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if (mode & RTLD_GLOBAL)
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add_to_global_resize (new);
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+ /* Unblock signals. Data structures are now consistent, and
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+ application code may run. */
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+ __libc_signal_restore_set (&args->original_signal_mask);
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+
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/* Run the initializer functions of new objects. Temporarily
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disable the exception handler, so that lazy binding failures are
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fatal. */
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@@ -834,6 +848,10 @@ no more namespaces available for dlmopen()"));
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args.argv = argv;
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args.env = env;
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+ /* Recursive lazy binding during manipulation of the dynamic loader
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+ structures may result in incorrect behavior. */
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+ __libc_signal_block_all (&args.original_signal_mask);
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+
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struct dl_exception exception;
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int errcode = _dl_catch_exception (&exception, dl_open_worker, &args);
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@@ -874,10 +892,16 @@ no more namespaces available for dlmopen()"));
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_dl_close_worker (args.map, true);
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+ /* Restore the signal mask. In the success case, this
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+ happens inside dl_open_worker. */
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+ __libc_signal_restore_set (&args.original_signal_mask);
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+
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/* All link_map_nodelete_pending objects should have been
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deleted at this point, which is why it is not necessary
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to reset the flag here. */
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}
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+ else
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+ __libc_signal_restore_set (&args.original_signal_mask);
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assert (_dl_debug_initialize (0, args.nsid)->r_state == RT_CONSISTENT);
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