From 689a62a4217fae78b9ce0db781dc2a421f2b1ab4 Mon Sep 17 00:00:00 2001 From: Michael Jeanson Date: Fri, 14 Feb 2025 13:54:22 -0500 Subject: [PATCH] nptl: clear the whole rseq area before registration Due to the extensible nature of the rseq area we can't explictly initialize fields that are not part of the ABI yet. It was agreed with upstream that all new fields will be documented as zero initialized by userspace. Future kernels configured with CONFIG_DEBUG_RSEQ will validate the content of all fields during registration. Replace the explicit field initialization with a memset of the whole rseq area which will cover fields as they are added to future kernels. Signed-off-by: Michael Jeanson Reviewed-by: Florian Weimer --- sysdeps/nptl/dl-tls_init_tp.c | 1 + sysdeps/unix/sysv/linux/rseq-internal.h | 11 +++++------ 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/sysdeps/nptl/dl-tls_init_tp.c b/sysdeps/nptl/dl-tls_init_tp.c index db99082b29..47566dce4f 100644 --- a/sysdeps/nptl/dl-tls_init_tp.c +++ b/sysdeps/nptl/dl-tls_init_tp.c @@ -23,6 +23,7 @@ #include #include #include +#include #define TUNABLE_NAMESPACE pthread #include diff --git a/sysdeps/unix/sysv/linux/rseq-internal.h b/sysdeps/unix/sysv/linux/rseq-internal.h index f89e784243..d2ab4cb829 100644 --- a/sysdeps/unix/sysv/linux/rseq-internal.h +++ b/sysdeps/unix/sysv/linux/rseq-internal.h @@ -108,13 +108,12 @@ rseq_register_current_thread (struct pthread *self, bool do_rseq) if (size < RSEQ_AREA_SIZE_INITIAL) size = RSEQ_AREA_SIZE_INITIAL; - /* Initialize the rseq fields that are read by the kernel on - registration, there is no guarantee that struct pthread is - cleared on all architectures. */ + /* Initialize the whole rseq area to zero prior to registration. */ + memset (RSEQ_SELF (), 0, size); + + /* Set the cpu_id field to RSEQ_CPU_ID_UNINITIALIZED, this is checked by + the kernel at registration when CONFIG_DEBUG_RSEQ is enabled. */ RSEQ_SETMEM (cpu_id, RSEQ_CPU_ID_UNINITIALIZED); - RSEQ_SETMEM (cpu_id_start, 0); - RSEQ_SETMEM (rseq_cs, 0); - RSEQ_SETMEM (flags, 0); int ret = INTERNAL_SYSCALL_CALL (rseq, RSEQ_SELF (), size, 0, RSEQ_SIG); if (!INTERNAL_SYSCALL_ERROR_P (ret))