[PATCH] x86: limit the fs segment to the pointer size
The fs segment is only used to get the global data pointer. If it is accessed beyond sizeof(new_gd->arch.gd_addr), it is a bug.
To specify the byte-granule limit size, drop the G bit, so the flag field is 0x8093 instead of 0xc093, and set the limit field to sizeof(new_gd->arch.gd_addr) - 1.
Signed-off-by: Masahiro Yamada masahiroy@kernel.org ---
arch/x86/cpu/i386/cpu.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/x86/cpu/i386/cpu.c b/arch/x86/cpu/i386/cpu.c index 2b27617ca3a4..72fefdd3adca 100644 --- a/arch/x86/cpu/i386/cpu.c +++ b/arch/x86/cpu/i386/cpu.c @@ -137,8 +137,9 @@ void arch_setup_gd(gd_t *new_gd)
/* FS: data, read/write, 4 GB, base (Global Data Pointer) */ new_gd->arch.gd_addr = new_gd; - gdt_addr[X86_GDT_ENTRY_32BIT_FS] = GDT_ENTRY(0xc093, - (ulong)&new_gd->arch.gd_addr, 0xfffff); + gdt_addr[X86_GDT_ENTRY_32BIT_FS] = GDT_ENTRY(0x8093, + (ulong)&new_gd->arch.gd_addr, + sizeof(new_gd->arch.gd_addr) - 1);
/* 16-bit CS: code, read/execute, 64 kB, base 0 */ gdt_addr[X86_GDT_ENTRY_16BIT_CS] = GDT_ENTRY(0x009b, 0, 0x0ffff);
On Wed, 8 Jan 2020 at 04:14, Masahiro Yamada masahiroy@kernel.org wrote:
The fs segment is only used to get the global data pointer. If it is accessed beyond sizeof(new_gd->arch.gd_addr), it is a bug.
To specify the byte-granule limit size, drop the G bit, so the flag field is 0x8093 instead of 0xc093, and set the limit field to sizeof(new_gd->arch.gd_addr) - 1.
Signed-off-by: Masahiro Yamada masahiroy@kernel.org
arch/x86/cpu/i386/cpu.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
Reviewed-by: Simon Glass sjg@chromium.org
On Wed, Jan 8, 2020 at 7:14 PM Masahiro Yamada masahiroy@kernel.org wrote:
The fs segment is only used to get the global data pointer. If it is accessed beyond sizeof(new_gd->arch.gd_addr), it is a bug.
To specify the byte-granule limit size, drop the G bit, so the flag field is 0x8093 instead of 0xc093, and set the limit field to sizeof(new_gd->arch.gd_addr) - 1.
Signed-off-by: Masahiro Yamada masahiroy@kernel.org
arch/x86/cpu/i386/cpu.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/x86/cpu/i386/cpu.c b/arch/x86/cpu/i386/cpu.c index 2b27617ca3a4..72fefdd3adca 100644 --- a/arch/x86/cpu/i386/cpu.c +++ b/arch/x86/cpu/i386/cpu.c @@ -137,8 +137,9 @@ void arch_setup_gd(gd_t *new_gd)
/* FS: data, read/write, 4 GB, base (Global Data Pointer) */
nits: this comment should be updated too
new_gd->arch.gd_addr = new_gd;
gdt_addr[X86_GDT_ENTRY_32BIT_FS] = GDT_ENTRY(0xc093,(ulong)&new_gd->arch.gd_addr, 0xfffff);
gdt_addr[X86_GDT_ENTRY_32BIT_FS] = GDT_ENTRY(0x8093,(ulong)&new_gd->arch.gd_addr,sizeof(new_gd->arch.gd_addr) - 1); /* 16-bit CS: code, read/execute, 64 kB, base 0 */ gdt_addr[X86_GDT_ENTRY_16BIT_CS] = GDT_ENTRY(0x009b, 0, 0x0ffff);--
Reviewed-by: Bin Meng bmeng.cn@gmail.com Tested-by: Bin Meng bmeng.cn@gmail.com
On Mon, Feb 3, 2020 at 12:41 PM Bin Meng bmeng.cn@gmail.com wrote:
On Wed, Jan 8, 2020 at 7:14 PM Masahiro Yamada masahiroy@kernel.org wrote:
The fs segment is only used to get the global data pointer. If it is accessed beyond sizeof(new_gd->arch.gd_addr), it is a bug.
To specify the byte-granule limit size, drop the G bit, so the flag field is 0x8093 instead of 0xc093, and set the limit field to sizeof(new_gd->arch.gd_addr) - 1.
Signed-off-by: Masahiro Yamada masahiroy@kernel.org
arch/x86/cpu/i386/cpu.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/x86/cpu/i386/cpu.c b/arch/x86/cpu/i386/cpu.c index 2b27617ca3a4..72fefdd3adca 100644 --- a/arch/x86/cpu/i386/cpu.c +++ b/arch/x86/cpu/i386/cpu.c @@ -137,8 +137,9 @@ void arch_setup_gd(gd_t *new_gd)
/* FS: data, read/write, 4 GB, base (Global Data Pointer) */nits: this comment should be updated too
Fixed the comments, and
new_gd->arch.gd_addr = new_gd;
gdt_addr[X86_GDT_ENTRY_32BIT_FS] = GDT_ENTRY(0xc093,(ulong)&new_gd->arch.gd_addr, 0xfffff);
gdt_addr[X86_GDT_ENTRY_32BIT_FS] = GDT_ENTRY(0x8093,(ulong)&new_gd->arch.gd_addr,sizeof(new_gd->arch.gd_addr) - 1); /* 16-bit CS: code, read/execute, 64 kB, base 0 */ gdt_addr[X86_GDT_ENTRY_16BIT_CS] = GDT_ENTRY(0x009b, 0, 0x0ffff);--
Reviewed-by: Bin Meng bmeng.cn@gmail.com Tested-by: Bin Meng bmeng.cn@gmail.com
applied to u-boot-x86, thanks!
participants (3)
-
Bin Meng -
Masahiro Yamada -
Simon Glass