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ptrace: make PTRACE_SEIZE set ptrace options specified in 'data' parameter
This can be used to close a few corner cases in strace where we get unwanted racy behavior after attach, but before we have a chance to set options (the notorious post-execve SIGTRAP comes to mind), and removes the need to track "did we set opts for this task" state in strace internals. While we are at it: Make it possible to extend SEIZE in the future with more functionality by passing non-zero 'addr' parameter. To that end, error out if 'addr' is non-zero. PTRACE_ATTACH did not (and still does not) have such check, and users (strace) do pass garbage there... let's avoid repeating this mistake with SEIZE. Set all task->ptrace bits in one operation - before this change, we were adding PT_SEIZED and PT_PTRACE_CAP with task->ptrace |= BIT ops. This was probably ok (not a bug), but let's be on a safer side. Changes since v2: use (unsigned long) casts instead of (long) ones, move PTRACE_SEIZE_DEVEL-related code to separate lines of code. Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com> Acked-by: Tejun Heo <tj@kernel.org> Cc: Pedro Alves <palves@redhat.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
86b6c1f301
commit
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1 changed files with 21 additions and 10 deletions
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@ -231,6 +231,7 @@ bool ptrace_may_access(struct task_struct *task, unsigned int mode)
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}
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}
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static int ptrace_attach(struct task_struct *task, long request,
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static int ptrace_attach(struct task_struct *task, long request,
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unsigned long addr,
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unsigned long flags)
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unsigned long flags)
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{
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{
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bool seize = (request == PTRACE_SEIZE);
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bool seize = (request == PTRACE_SEIZE);
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@ -238,19 +239,29 @@ static int ptrace_attach(struct task_struct *task, long request,
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/*
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/*
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* SEIZE will enable new ptrace behaviors which will be implemented
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* SEIZE will enable new ptrace behaviors which will be implemented
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* gradually. SEIZE_DEVEL is used to prevent applications
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* gradually. SEIZE_DEVEL bit is used to prevent applications
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* expecting full SEIZE behaviors trapping on kernel commits which
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* expecting full SEIZE behaviors trapping on kernel commits which
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* are still in the process of implementing them.
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* are still in the process of implementing them.
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*
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*
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* Only test programs for new ptrace behaviors being implemented
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* Only test programs for new ptrace behaviors being implemented
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* should set SEIZE_DEVEL. If unset, SEIZE will fail with -EIO.
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* should set SEIZE_DEVEL. If unset, SEIZE will fail with -EIO.
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*
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*
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* Once SEIZE behaviors are completely implemented, this flag and
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* Once SEIZE behaviors are completely implemented, this flag
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* the following test will be removed.
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* will be removed.
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*/
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*/
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retval = -EIO;
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retval = -EIO;
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if (seize && !(flags & PTRACE_SEIZE_DEVEL))
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if (seize) {
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goto out;
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if (addr != 0)
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goto out;
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if (!(flags & PTRACE_SEIZE_DEVEL))
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goto out;
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flags &= ~(unsigned long)PTRACE_SEIZE_DEVEL;
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if (flags & ~(unsigned long)PTRACE_O_MASK)
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goto out;
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flags = PT_PTRACED | PT_SEIZED | (flags << PT_OPT_FLAG_SHIFT);
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} else {
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flags = PT_PTRACED;
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}
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audit_ptrace(task);
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audit_ptrace(task);
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@ -282,11 +293,11 @@ static int ptrace_attach(struct task_struct *task, long request,
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if (task->ptrace)
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if (task->ptrace)
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goto unlock_tasklist;
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goto unlock_tasklist;
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task->ptrace = PT_PTRACED;
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if (seize)
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if (seize)
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task->ptrace |= PT_SEIZED;
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flags |= PT_SEIZED;
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if (ns_capable(task_user_ns(task), CAP_SYS_PTRACE))
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if (ns_capable(task_user_ns(task), CAP_SYS_PTRACE))
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task->ptrace |= PT_PTRACE_CAP;
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flags |= PT_PTRACE_CAP;
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task->ptrace = flags;
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__ptrace_link(task, current);
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__ptrace_link(task, current);
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@ -879,7 +890,7 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr,
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}
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}
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if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {
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if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {
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ret = ptrace_attach(child, request, data);
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ret = ptrace_attach(child, request, addr, data);
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/*
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/*
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* Some architectures need to do book-keeping after
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* Some architectures need to do book-keeping after
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* a ptrace attach.
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* a ptrace attach.
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@ -1022,7 +1033,7 @@ asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
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}
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}
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if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {
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if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {
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ret = ptrace_attach(child, request, data);
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ret = ptrace_attach(child, request, addr, data);
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/*
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/*
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* Some architectures need to do book-keeping after
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* Some architectures need to do book-keeping after
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* a ptrace attach.
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* a ptrace attach.
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