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)

diff --git a/NEWS b/NEWS
index 3634e0c8b5331e63223b43cb7ec48543fb6e9de1..81d986567ea4e2588968f7608513b4867410b1e7 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -53,6 +53,7 @@ The following bugs are resolved with this release:
   [30515] _dl_find_object incorrectly returns 1 during early startup
   [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
 \f
 Version 2.37
 

diff --git a/sysdeps/x86_64/dl-tlsdesc.S b/sysdeps/x86_64/dl-tlsdesc.S
index c4823547d7b81d0f9b6adb96c5c748a1835c2e8e..4579424bf7e98d0a4e15df4ae5aab8b610875a70 100644 (file)
--- 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: