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authorGabriel Krisman Bertazi <krisman@collabora.com>2021-02-03 21:00:48 +0300
committerThomas Gleixner <tglx@linutronix.de>2021-02-06 02:21:42 +0300
commit6342adcaa683c2b705c24ed201dc11b35854c88d (patch)
treed75d12186c1d9e79168bdd0b84740d7701bee408 /kernel/entry
parent1048ba83fb1c00cd24172e23e8263972f6b5d9ac (diff)
downloadlinux-6342adcaa683c2b705c24ed201dc11b35854c88d.tar.xz
entry: Ensure trap after single-step on system call return
Commit 299155244770 ("entry: Drop usage of TIF flags in the generic syscall code") introduced a bug on architectures using the generic syscall entry code, in which processes stopped by PTRACE_SYSCALL do not trap on syscall return after receiving a TIF_SINGLESTEP. The reason is that the meaning of TIF_SINGLESTEP flag is overloaded to cause the trap after a system call is executed, but since the above commit, the syscall call handler only checks for the SYSCALL_WORK flags on the exit work. Split the meaning of TIF_SINGLESTEP such that it only means single-step mode, and create a new type of SYSCALL_WORK to request a trap immediately after a syscall in single-step mode. In the current implementation, the SYSCALL_WORK flag shadows the TIF_SINGLESTEP flag for simplicity. Update x86 to flip this bit when a tracer enables single stepping. Fixes: 299155244770 ("entry: Drop usage of TIF flags in the generic syscall code") Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Kyle Huey <me@kylehuey.com> Link: https://lore.kernel.org/r/87h7mtc9pr.fsf_-_@collabora.com
Diffstat (limited to 'kernel/entry')
-rw-r--r--kernel/entry/common.c12
1 files changed, 2 insertions, 10 deletions
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 6dd82be60df8..f9d491b17b78 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -209,15 +209,9 @@ static void exit_to_user_mode_prepare(struct pt_regs *regs)
lockdep_sys_exit();
}
-#ifndef _TIF_SINGLESTEP
-static inline bool report_single_step(unsigned long work)
-{
- return false;
-}
-#else
/*
* If SYSCALL_EMU is set, then the only reason to report is when
- * TIF_SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall
+ * SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall
* instruction has been already reported in syscall_enter_from_user_mode().
*/
static inline bool report_single_step(unsigned long work)
@@ -225,10 +219,8 @@ static inline bool report_single_step(unsigned long work)
if (work & SYSCALL_WORK_SYSCALL_EMU)
return false;
- return !!(current_thread_info()->flags & _TIF_SINGLESTEP);
+ return work & SYSCALL_WORK_SYSCALL_EXIT_TRAP;
}
-#endif
-
static void syscall_exit_work(struct pt_regs *regs, unsigned long work)
{