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From 968c983d43bc51f719f3e7a0fcb1bb8669b5f7c4 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Wed, 20 Dec 2023 19:42:12 -0800
Subject: [PATCH 5/9] x86-64: Fix the tcb field load for x32 [BZ #31185]
_dl_tlsdesc_undefweak and _dl_tlsdesc_dynamic access the thread pointer
via the tcb field in TCB:
_dl_tlsdesc_undefweak:
_CET_ENDBR
movq 8(%rax), %rax
subq %fs:0, %rax
ret
_dl_tlsdesc_dynamic:
...
subq %fs:0, %rax
movq -8(%rsp), %rdi
ret
Since the tcb field in TCB is a pointer, %fs:0 is a 32-bit location,
not 64-bit. It should use "sub %fs:0, %RAX_LP" instead. Since
_dl_tlsdesc_undefweak returns ptrdiff_t and _dl_make_tlsdesc_dynamic
returns void *, RAX_LP is appropriate here for x32 and x86-64. This
fixes BZ #31185.
(cherry picked from commit 81be2a61dafc168327c1639e97b6dae128c7ccf3)
---
NEWS | 1 +
sysdeps/x86_64/dl-tlsdesc.S | 4 ++--
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/NEWS b/NEWS
index 71057e4793..6fbb8a9e1d 100644
--- a/NEWS
+++ b/NEWS
@@ -38,6 +38,7 @@ The following bugs are resolved with this release:
-D_FILE_OFFSET_BITS=64
[30842] Stack read overflow in getaddrinfo in no-aaaa mode (CVE-2023-4527)
[31184] FAIL: elf/tst-tlsgap
+ [31185] Incorrect thread point access in _dl_tlsdesc_undefweak and _dl_tlsdesc_dynamic
Version 2.38
diff --git a/sysdeps/x86_64/dl-tlsdesc.S b/sysdeps/x86_64/dl-tlsdesc.S
index c4823547d7..4579424bf7 100644
--- a/sysdeps/x86_64/dl-tlsdesc.S
+++ b/sysdeps/x86_64/dl-tlsdesc.S
@@ -61,7 +61,7 @@ _dl_tlsdesc_return:
_dl_tlsdesc_undefweak:
_CET_ENDBR
movq 8(%rax), %rax
- subq %fs:0, %rax
+ sub %fs:0, %RAX_LP
ret
cfi_endproc
.size _dl_tlsdesc_undefweak, .-_dl_tlsdesc_undefweak
@@ -116,7 +116,7 @@ _dl_tlsdesc_dynamic:
addq TLSDESC_MODOFF(%rdi), %rax
.Lret:
movq -16(%rsp), %rsi
- subq %fs:0, %rax
+ sub %fs:0, %RAX_LP
movq -8(%rsp), %rdi
ret
.Lslow:
--
2.33.0
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