From 84b2789d61156db0224724806b20110c0d34b07c Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Wed, 13 Jan 2021 22:09:42 +0100 Subject: [PATCH] um: separate child and parent errors in clone stub If the two are mixed up, then it looks as though the parent returned an error if the child failed (before) the mmap(), and then the resulting process never gets killed. Fix this by splitting the child and parent errors, reporting and using them appropriately. Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger --- arch/um/include/shared/skas/stub-data.h | 2 +- arch/um/kernel/skas/clone.c | 25 +++++++++++-------------- arch/um/os-Linux/skas/process.c | 23 +++++++++++++---------- arch/x86/um/shared/sysdep/stub_32.h | 2 +- arch/x86/um/shared/sysdep/stub_64.h | 2 +- 5 files changed, 27 insertions(+), 27 deletions(-) diff --git a/arch/um/include/shared/skas/stub-data.h b/arch/um/include/shared/skas/stub-data.h index 6b01d97..5e3ade3 100644 --- a/arch/um/include/shared/skas/stub-data.h +++ b/arch/um/include/shared/skas/stub-data.h @@ -11,7 +11,7 @@ struct stub_data { unsigned long offset; int fd; - long err; + long parent_err, child_err; }; #endif diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c index bfb70c4..7c592c7 100644 --- a/arch/um/kernel/skas/clone.c +++ b/arch/um/kernel/skas/clone.c @@ -24,29 +24,26 @@ void __attribute__ ((__section__ (".__syscall_stub"))) stub_clone_handler(void) { - struct stub_data *data = (struct stub_data *) STUB_DATA; + int stack; + struct stub_data *data = (void *) ((unsigned long)&stack & ~(UM_KERN_PAGE_SIZE - 1)); long err; err = stub_syscall2(__NR_clone, CLONE_PARENT | CLONE_FILES | SIGCHLD, - STUB_DATA + UM_KERN_PAGE_SIZE / 2 - sizeof(void *)); - if (err != 0) - goto out; + (unsigned long)data + UM_KERN_PAGE_SIZE / 2 - sizeof(void *)); + if (err) { + data->parent_err = err; + goto done; + } err = stub_syscall4(__NR_ptrace, PTRACE_TRACEME, 0, 0, 0); - if (err) - goto out; + if (err) { + data->child_err = err; + goto done; + } remap_stack(data->fd, data->offset); goto done; - out: - /* - * save current result. - * Parent: pid; - * child: retcode of mmap already saved and it jumps around this - * assignment - */ - data->err = err; done: trap_myself(); } diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c index d910e25..623b0ae 100644 --- a/arch/um/os-Linux/skas/process.c +++ b/arch/um/os-Linux/skas/process.c @@ -545,8 +545,14 @@ int copy_context_skas0(unsigned long new_stack, int pid) * and child's mmap2 calls */ *data = ((struct stub_data) { - .offset = MMAP_OFFSET(new_offset), - .fd = new_fd + .offset = MMAP_OFFSET(new_offset), + .fd = new_fd, + .parent_err = -ESRCH, + .child_err = 0, + }); + + *child_data = ((struct stub_data) { + .child_err = -ESRCH, }); err = ptrace_setregs(pid, thread_regs); @@ -564,9 +570,6 @@ int copy_context_skas0(unsigned long new_stack, int pid) return err; } - /* set a well known return code for detection of child write failure */ - child_data->err = 12345678; - /* * Wait, until parent has finished its work: read child's pid from * parent's stack, and check, if bad result. @@ -581,7 +584,7 @@ int copy_context_skas0(unsigned long new_stack, int pid) wait_stub_done(pid); - pid = data->err; + pid = data->parent_err; if (pid < 0) { printk(UM_KERN_ERR "copy_context_skas0 - stub-parent reports " "error %d\n", -pid); @@ -593,10 +596,10 @@ int copy_context_skas0(unsigned long new_stack, int pid) * child's stack and check it. */ wait_stub_done(pid); - if (child_data->err != STUB_DATA) { - printk(UM_KERN_ERR "copy_context_skas0 - stub-child reports " - "error %ld\n", child_data->err); - err = child_data->err; + if (child_data->child_err != STUB_DATA) { + printk(UM_KERN_ERR "copy_context_skas0 - stub-child %d reports " + "error %ld\n", pid, data->child_err); + err = data->child_err; goto out_kill; } diff --git a/arch/x86/um/shared/sysdep/stub_32.h b/arch/x86/um/shared/sysdep/stub_32.h index 51fd256..8ea6921 100644 --- a/arch/x86/um/shared/sysdep/stub_32.h +++ b/arch/x86/um/shared/sysdep/stub_32.h @@ -86,7 +86,7 @@ static inline void remap_stack(int fd, unsigned long offset) "d" (PROT_READ | PROT_WRITE), "S" (MAP_FIXED | MAP_SHARED), "D" (fd), "a" (offset), - "i" (&((struct stub_data *) STUB_DATA)->err) + "i" (&((struct stub_data *) STUB_DATA)->child_err) : "memory"); } diff --git a/arch/x86/um/shared/sysdep/stub_64.h b/arch/x86/um/shared/sysdep/stub_64.h index 994df93..b7b8b8e 100644 --- a/arch/x86/um/shared/sysdep/stub_64.h +++ b/arch/x86/um/shared/sysdep/stub_64.h @@ -92,7 +92,7 @@ static inline void remap_stack(long fd, unsigned long offset) "d" (PROT_READ | PROT_WRITE), "g" (MAP_FIXED | MAP_SHARED), "g" (fd), "g" (offset), - "i" (&((struct stub_data *) STUB_DATA)->err) + "i" (&((struct stub_data *) STUB_DATA)->child_err) : __syscall_clobber, "r10", "r8", "r9" ); } -- 2.7.4