diff --git a/glibc-rseq-disable.patch b/glibc-rseq-disable.patch
new file mode 100644
index 0000000..40090a7
--- /dev/null
+++ b/glibc-rseq-disable.patch
@@ -0,0 +1,125 @@
+Disable rseq integration until the Firefox sandbox supports rseq.
+
+Sandbox is incompatible with rseq registration
+<https://bugzilla.mozilla.org/show_bug.cgi?id=1651701>
+
+diff --git a/elf/libc_early_init.c b/elf/libc_early_init.c
+index 86da66d5e01af08f..fd779941e7180fb6 100644
+--- a/elf/libc_early_init.c
++++ b/elf/libc_early_init.c
+@@ -28,8 +28,9 @@ __libc_early_init (_Bool initial)
+   __ctype_init ();
+ 
+   /* Register rseq ABI to the kernel for the main program's libc.   */
++  rseq_active_init ();
+   if (initial)
+-    rseq_register_current_thread ();
++      rseq_register_current_thread ();
+ 
+   /* Only the outer namespace is marked as single-threaded.  */
+   __libc_single_threaded = initial;
+diff --git a/sysdeps/unix/sysv/linux/Versions b/sysdeps/unix/sysv/linux/Versions
+index f72741b7e5afb22a..a730077142f0e20a 100644
+--- a/sysdeps/unix/sysv/linux/Versions
++++ b/sysdeps/unix/sysv/linux/Versions
+@@ -171,6 +171,8 @@ libc {
+     __rseq_abi;
+   }
+   GLIBC_PRIVATE {
++    __rseq_active;
++
+     # functions used in other libraries
+     __syscall_rt_sigqueueinfo;
+     __open_nocancel;
+diff --git a/sysdeps/unix/sysv/linux/rseq-internal.h b/sysdeps/unix/sysv/linux/rseq-internal.h
+index 8f6772ca1deada89..acaf033be465facd 100644
+--- a/sysdeps/unix/sysv/linux/rseq-internal.h
++++ b/sysdeps/unix/sysv/linux/rseq-internal.h
+@@ -23,13 +23,29 @@
+ #include <kernel-features.h>
+ #include <stdio.h>
+ #include <sys/rseq.h>
++#include <unistd.h>
+ 
+ #ifdef RSEQ_SIG
++
++extern _Bool __rseq_active;
++
++static inline void
++rseq_active_init (void)
++{
++  __rseq_active = __access ("/etc/glibc.rseq.enabled", F_OK) == 0;
++}
++
+ static inline void
+ rseq_register_current_thread (void)
+ {
+   int ret;
+ 
++  if (!__rseq_active)
++    {
++      __rseq_abi.cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED;
++      return;
++    }
++
+   if (__rseq_abi.cpu_id != RSEQ_CPU_ID_UNINITIALIZED)
+     __libc_fatal ("glibc fatal error: "
+                   "rseq already initialized for this thread\n");
+@@ -64,6 +80,11 @@ rseq_register_current_thread (void)
+     }
+ }
+ #else /* RSEQ_SIG */
++static inline void
++rseq_active_init (void)
++{
++}
++
+ static inline void
+ rseq_register_current_thread (void)
+ {
+diff --git a/sysdeps/unix/sysv/linux/rseq-sym.c b/sysdeps/unix/sysv/linux/rseq-sym.c
+index 090093408f1a4b3f..78d3a9dd8355436b 100644
+--- a/sysdeps/unix/sysv/linux/rseq-sym.c
++++ b/sysdeps/unix/sysv/linux/rseq-sym.c
+@@ -19,8 +19,11 @@
+ #include <stdint.h>
+ #include <kernel-features.h>
+ #include <sys/rseq.h>
++#include <rseq-internal.h>
+ 
+ __thread struct rseq __rseq_abi =
+   {
+     .cpu_id = RSEQ_CPU_ID_UNINITIALIZED,
+   };
++
++_Bool __rseq_active __attribute__ ((nocommon));
+diff --git a/sysdeps/unix/sysv/linux/tst-rseq-nptl.c b/sysdeps/unix/sysv/linux/tst-rseq-nptl.c
+index 5e788dcfa9eef8ef..ed846e9f5d5a5f4e 100644
+--- a/sysdeps/unix/sysv/linux/tst-rseq-nptl.c
++++ b/sysdeps/unix/sysv/linux/tst-rseq-nptl.c
+@@ -250,6 +250,10 @@ do_rseq_test (void)
+ static int
+ do_test (void)
+ {
++  extern _Bool __rseq_active;
++  if (!__rseq_active)
++    FAIL_UNSUPPORTED ("/etc/glibc.rseq.enabled missing, test disabled");
++
+   return do_rseq_test ();
+ }
+ 
+diff --git a/sysdeps/unix/sysv/linux/tst-rseq.c b/sysdeps/unix/sysv/linux/tst-rseq.c
+index aa902fb26a64f917..60eaab4bc13d1275 100644
+--- a/sysdeps/unix/sysv/linux/tst-rseq.c
++++ b/sysdeps/unix/sysv/linux/tst-rseq.c
+@@ -57,6 +57,10 @@ do_rseq_test (void)
+ static int
+ do_test (void)
+ {
++  extern _Bool __rseq_active;
++  if (!__rseq_active)
++    FAIL_UNSUPPORTED ("/etc/glibc.rseq.enabled missing, test disabled");
++
+   do_rseq_test ();
+   return 0;
+ }
diff --git a/glibc.spec b/glibc.spec
index d0d7eb3..1e62745 100644
--- a/glibc.spec
+++ b/glibc.spec
@@ -96,7 +96,7 @@
 Summary: The GNU libc libraries
 Name: glibc
 Version: %{glibcversion}
-Release: 18%{?dist}
+Release: 19%{?dist}
 
 # In general, GPLv2+ is used by programs, LGPLv2+ is used for
 # libraries.
@@ -167,6 +167,7 @@ Patch17: glibc-cs-path.patch
 Patch18: glibc-c-utf8-locale.patch
 Patch23: glibc-python3.patch
 Patch29: glibc-fedora-nsswitch.patch
+Patch30: glibc-rseq-disable.patch
 
 ##############################################################################
 # Continued list of core "glibc" package information:
@@ -2017,6 +2018,9 @@ fi
 %files -f compat-libpthread-nonshared.filelist -n compat-libpthread-nonshared
 
 %changelog
+* Fri Jul 10 2020 Florian Weimer <fweimer@redhat.com> - 2.31.9000-19
+- Disable rseq registration by default to help Firefox (#1855729)
+
 * Thu Jul 09 2020 Florian Weimer <fweimer@redhat.com> - 2.31.9000-18
 - Auto-sync with upstream branch master,
   commit ffb17e7ba3a5ba9632cee97330b325072fbe41dd: