[PATCH RFC POC 06/50] arm64: commit fds on syscall exit

[Christian Brauner]

Add TIF_FD_SLOTS to the syscall work bits. el0_svc_common() rereads
the flags after the system call and takes the trace exit for any of
them. So a task that reserved descriptors ends up in
syscall_trace_exit() which commits them before audit and the ptrace exit
stop.

Signed-off-by: Christian Brauner (Amutable) <brauner at kernel.org>
---
 arch/arm64/include/asm/thread_info.h | 4 +++-
 arch/arm64/kernel/ptrace.c           | 4 ++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index 5d7fe3e153c8..e48006eb98a8 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -74,6 +74,7 @@ void arch_setup_new_exec(void);
 #define TIF_SECCOMP		11	/* syscall secure computing */
 #define TIF_SYSCALL_EMU		12	/* syscall emulation active */
 #define TIF_PATCH_PENDING	13	/* pending live patching update */
+#define TIF_FD_SLOTS		14	/* syscall prepared descriptors */
 #define TIF_MEMDIE		18	/* is terminating due to OOM killer */
 #define TIF_FREEZE		19
 #define TIF_RESTORE_SIGMASK	20
@@ -107,10 +108,11 @@ void arch_setup_new_exec(void);
 #define _TIF_MTE_ASYNC_FAULT	(1 << TIF_MTE_ASYNC_FAULT)
 #define _TIF_NOTIFY_SIGNAL	(1 << TIF_NOTIFY_SIGNAL)
 #define _TIF_TSC_SIGSEGV	(1 << TIF_TSC_SIGSEGV)
+#define _TIF_FD_SLOTS		(1 << TIF_FD_SLOTS)
 
 #define _TIF_SYSCALL_WORK	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
 				 _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
-				 _TIF_SYSCALL_EMU)
+				 _TIF_SYSCALL_EMU | _TIF_FD_SLOTS)
 
 #ifdef CONFIG_SHADOW_CALL_STACK
 #define INIT_SCS							\
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index f743cbec1c3a..3bedfed977d4 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -28,6 +28,7 @@
 #include <linux/hw_breakpoint.h>
 #include <linux/regset.h>
 #include <linux/elf.h>
+#include <linux/file.h>
 #include <linux/rseq.h>
 
 #include <asm/compat.h>
@@ -2486,6 +2487,9 @@ void syscall_trace_exit(struct pt_regs *regs)
 {
 	unsigned long flags = read_thread_flags();
 
+	if (flags & _TIF_FD_SLOTS)
+		fd_slots_commit(regs);
+
 	audit_syscall_exit(regs);
 
 	if (flags & _TIF_SYSCALL_TRACEPOINT)

-- 
2.53.0