[GIT PULL] x86 fixes

Ingo Molnar
2016-08-06T21:49:09Z

Linus,

Please pull the latest x86-urgent-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-urgent-for-linus

# HEAD: f7d665627e103e82d34306c7d3f6f46f387c0d8b x86/syscalls/64: Add compat_sys_keyctl for 32-bit userspace

Two fixes and a cleanup-fix, to the syscall entry code and to ptrace.

Thanks,

Ingo

------------------>
Andy Lutomirski (2):
x86/vdso: Error out if the vDSO isn't a valid DSO
x86/ptrace: Stop setting TS_COMPAT in ptrace code

David Howells (1):
x86/syscalls/64: Add compat_sys_keyctl for 32-bit userspace

arch/x86/entry/common.c | 6 +++++-
arch/x86/entry/syscalls/syscall_32.tbl | 2 +-
arch/x86/entry/vdso/vdso2c.h | 6 ++++++
arch/x86/include/asm/syscall.h | 5 +----
arch/x86/include/asm/thread_info.h | 3 +++
arch/x86/kernel/ptrace.c | 15 +++++++++------
arch/x86/kernel/signal.c | 26 ++++++++++++++++++++++++--
7 files changed, 49 insertions(+), 14 deletions(-)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 9e1e27d31c6d..be8c403f8117 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -270,8 +270,12 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
* handling, because syscall restart has a fixup for compat
* syscalls. The fixup is exercised by the ptrace_syscall_32
* selftest.
+ *
+ * We also need to clear TS_REGS_POKED_I386: the 32-bit tracer
+ * special case only applies after poking regs and before the
+ * very next return to user mode.
*/
- ti->status &= ~TS_COMPAT;
+ ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
#endif

user_enter_irqoff();
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 4cddd17153fb..f848572169ea 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -294,7 +294,7 @@
# 285 sys_setaltroot
286 i386 add_key sys_add_key
287 i386 request_key sys_request_key
-288 i386 keyctl sys_keyctl
+288 i386 keyctl sys_keyctl compat_sys_keyctl
289 i386 ioprio_set sys_ioprio_set
290 i386 ioprio_get sys_ioprio_get
291 i386 inotify_init sys_inotify_init
diff --git a/arch/x86/entry/vdso/vdso2c.h b/arch/x86/entry/vdso/vdso2c.h
index 63a03bb91497..4f741192846d 100644
--- a/arch/x86/entry/vdso/vdso2c.h
+++ b/arch/x86/entry/vdso/vdso2c.h
@@ -22,6 +22,9 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len,

ELF(Phdr) *pt = (ELF(Phdr) *)(raw_addr + GET_LE(&hdr->e_phoff));

+ if (hdr->e_type != ET_DYN)
+ fail("input is not a shared object\n");
+
/* Walk the segment table. */
for (i = 0; i < GET_LE(&hdr->e_phnum); i++) {
if (GET_LE(&pt[i].p_type) == PT_LOAD) {
@@ -49,6 +52,9 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
if (stripped_len < load_size)
fail("stripped input is too short\n");

+ if (!dyn)
+ fail("input has no PT_DYNAMIC section -- your toolchain is buggy\n");
+
/* Walk the dynamic table */
for (i = 0; dyn + i < dyn_end &&
GET_LE(&dyn[i].d_tag) != DT_NULL; i++) {
diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
index 999b7cd2e78c..4e23dd15c661 100644
--- a/arch/x86/include/asm/syscall.h
+++ b/arch/x86/include/asm/syscall.h
@@ -60,7 +60,7 @@ static inline long syscall_get_error(struct task_struct *task,
* TS_COMPAT is set for 32-bit syscall entries and then
* remains set until we return to user mode.
*/
- if (task_thread_info(task)->status & TS_COMPAT)
+ if (task_thread_info(task)->status & (TS_COMPAT|TS_I386_REGS_POKED))
/*
* Sign-extend the value so (int)-EFOO becomes (long)-EFOO
* and will match correctly in comparisons.
@@ -239,9 +239,6 @@ static inline int syscall_get_arch(void)
* TS_COMPAT is set for 32-bit syscall entry and then
* remains set until we return to user mode.
*
- * TIF_IA32 tasks should always have TS_COMPAT set at
- * system call time.
- *
* x32 tasks should be considered AUDIT_ARCH_X86_64.
*/
if (task_thread_info(current)->status & TS_COMPAT)
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 89bff044a6f5..f856c590c309 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -219,6 +219,9 @@ static inline unsigned long current_stack_pointer(void)
* have to worry about atomic accesses.
*/
#define TS_COMPAT 0x0002 /* 32bit syscall active (64BIT)*/
+#ifdef CONFIG_COMPAT
+#define TS_I386_REGS_POKED 0x0004 /* regs poked by 32-bit ptracer */
+#endif
#define TS_RESTORE_SIGMASK 0x0008 /* restore signal mask in do_signal() */

#ifndef __ASSEMBLY__
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 600edd225e81..f79576a541ff 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -923,15 +923,18 @@ static int putreg32(struct task_struct *child, unsigned regno, u32 value)

case offsetof(struct user32, regs.orig_eax):
/*
- * A 32-bit debugger setting orig_eax means to restore
- * the state of the task restarting a 32-bit syscall.
- * Make sure we interpret the -ERESTART* codes correctly
- * in case the task is not actually still sitting at the
- * exit from a 32-bit syscall with TS_COMPAT still set.
+ * Warning: bizarre corner case fixup here. A 32-bit
+ * debugger setting orig_eax to -1 wants to disable
+ * syscall restart. Make sure that the syscall
+ * restart code sign-extends orig_ax. Also make sure
+ * we interpret the -ERESTART* codes correctly if
+ * loaded into regs->ax in case the task is not
+ * actually still sitting at the exit from a 32-bit
+ * syscall with TS_COMPAT still set.
*/
regs->orig_ax = value;
if (syscall_get_nr(child, regs) >= 0)
- task_thread_info(child)->status |= TS_COMPAT;
+ task_thread_info(child)->status |= TS_I386_REGS_POKED;
break;

case offsetof(struct user32, regs.eflags):
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 22cc2f9f8aec..9747a6358949 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -760,8 +760,30 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)

static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
{
-#ifdef CONFIG_X86_64
- if (in_ia32_syscall())
+ /*
+ * This function is fundamentally broken as currently
+ * implemented.
+ *
+ * The idea is that we want to trigger a call to the
+ * restart_block() syscall and that we want in_ia32_syscall(),
+ * in_x32_syscall(), etc. to match whatever they were in the
+ * syscall being restarted. We assume that the syscall
+ * instruction at (regs->ip - 2) matches whatever syscall
+ * instruction we used to enter in the first place.
+ *
+ * The problem is that we can get here when ptrace pokes
+ * syscall-like values into regs even if we're not in a syscall
+ * at all.
+ *
+ * For now, we maintain historical behavior and guess based on
+ * stored state. We could do better by saving the actual
+ * syscall arch in restart_block or (with caveats on x32) by
+ * checking if regs->ip points to 'int $0x80'. The current
+ * behavior is incorrect if a tracer has a different bitness
+ * than the tracee.
+ */
+#ifdef CONFIG_IA32_EMULATION
+ if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED))
return __NR_ia32_restart_syscall;
#endif
#ifdef CONFIG_X86_X32_ABI