Commit aa9147c9 authored by Denys Vlasenko's avatar Denys Vlasenko Committed by Linus Torvalds

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: default avatarDenys Vlasenko <vda.linux@googlemail.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Cc: Pedro Alves <palves@redhat.com>
Reviewed-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 86b6c1f3
...@@ -231,6 +231,7 @@ bool ptrace_may_access(struct task_struct *task, unsigned int mode) ...@@ -231,6 +231,7 @@ bool ptrace_may_access(struct task_struct *task, unsigned int mode)
} }
static int ptrace_attach(struct task_struct *task, long request, static int ptrace_attach(struct task_struct *task, long request,
unsigned long addr,
unsigned long flags) unsigned long flags)
{ {
bool seize = (request == PTRACE_SEIZE); bool seize = (request == PTRACE_SEIZE);
...@@ -238,19 +239,29 @@ static int ptrace_attach(struct task_struct *task, long request, ...@@ -238,19 +239,29 @@ static int ptrace_attach(struct task_struct *task, long request,
/* /*
* SEIZE will enable new ptrace behaviors which will be implemented * SEIZE will enable new ptrace behaviors which will be implemented
* gradually. SEIZE_DEVEL is used to prevent applications * gradually. SEIZE_DEVEL bit is used to prevent applications
* expecting full SEIZE behaviors trapping on kernel commits which * expecting full SEIZE behaviors trapping on kernel commits which
* are still in the process of implementing them. * are still in the process of implementing them.
* *
* Only test programs for new ptrace behaviors being implemented * Only test programs for new ptrace behaviors being implemented
* should set SEIZE_DEVEL. If unset, SEIZE will fail with -EIO. * should set SEIZE_DEVEL. If unset, SEIZE will fail with -EIO.
* *
* Once SEIZE behaviors are completely implemented, this flag and * Once SEIZE behaviors are completely implemented, this flag
* the following test will be removed. * will be removed.
*/ */
retval = -EIO; retval = -EIO;
if (seize && !(flags & PTRACE_SEIZE_DEVEL)) if (seize) {
goto out; if (addr != 0)
goto out;
if (!(flags & PTRACE_SEIZE_DEVEL))
goto out;
flags &= ~(unsigned long)PTRACE_SEIZE_DEVEL;
if (flags & ~(unsigned long)PTRACE_O_MASK)
goto out;
flags = PT_PTRACED | PT_SEIZED | (flags << PT_OPT_FLAG_SHIFT);
} else {
flags = PT_PTRACED;
}
audit_ptrace(task); audit_ptrace(task);
...@@ -282,11 +293,11 @@ static int ptrace_attach(struct task_struct *task, long request, ...@@ -282,11 +293,11 @@ static int ptrace_attach(struct task_struct *task, long request,
if (task->ptrace) if (task->ptrace)
goto unlock_tasklist; goto unlock_tasklist;
task->ptrace = PT_PTRACED;
if (seize) if (seize)
task->ptrace |= PT_SEIZED; flags |= PT_SEIZED;
if (ns_capable(task_user_ns(task), CAP_SYS_PTRACE)) if (ns_capable(task_user_ns(task), CAP_SYS_PTRACE))
task->ptrace |= PT_PTRACE_CAP; flags |= PT_PTRACE_CAP;
task->ptrace = flags;
__ptrace_link(task, current); __ptrace_link(task, current);
...@@ -879,7 +890,7 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr, ...@@ -879,7 +890,7 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr,
} }
if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) { if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {
ret = ptrace_attach(child, request, data); ret = ptrace_attach(child, request, addr, data);
/* /*
* Some architectures need to do book-keeping after * Some architectures need to do book-keeping after
* a ptrace attach. * a ptrace attach.
...@@ -1022,7 +1033,7 @@ asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid, ...@@ -1022,7 +1033,7 @@ asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
} }
if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) { if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {
ret = ptrace_attach(child, request, data); ret = ptrace_attach(child, request, addr, data);
/* /*
* Some architectures need to do book-keeping after * Some architectures need to do book-keeping after
* a ptrace attach. * a ptrace attach.
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment