From: Jann Horn jannh@google.com
commit ee1fee900537b5d9560e9f937402de5ddc8412f3 upstream.
Setting PTRACE_O_SUSPEND_SECCOMP is supposed to be a highly privileged operation because it allows the tracee to completely bypass all seccomp filters on kernels with CONFIG_CHECKPOINT_RESTORE=y. It is only supposed to be settable by a process with global CAP_SYS_ADMIN, and only if that process is not subject to any seccomp filters at all.
However, while these permission checks were done on the PTRACE_SETOPTIONS path, they were missing on the PTRACE_SEIZE path, which also sets user-specified ptrace flags.
Move the permissions checks out into a helper function and let both ptrace_attach() and ptrace_setoptions() call it.
Cc: stable@kernel.org Fixes: 13c4a90119d2 ("seccomp: add ptrace options for suspend/resume") Signed-off-by: Jann Horn jannh@google.com Link: https://lkml.kernel.org/r/20220319010838.1386861-1-jannh@google.com Signed-off-by: Eric W. Biederman ebiederm@xmission.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/ptrace.c | 47 ++++++++++++++++++++++++++++++++--------------- 1 file changed, 32 insertions(+), 15 deletions(-)
--- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -364,6 +364,26 @@ bool ptrace_may_access(struct task_struc return !err; }
+static int check_ptrace_options(unsigned long data) +{ + if (data & ~(unsigned long)PTRACE_O_MASK) + return -EINVAL; + + if (unlikely(data & PTRACE_O_SUSPEND_SECCOMP)) { + if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) || + !IS_ENABLED(CONFIG_SECCOMP)) + return -EINVAL; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + if (seccomp_mode(¤t->seccomp) != SECCOMP_MODE_DISABLED || + current->ptrace & PT_SUSPEND_SECCOMP) + return -EPERM; + } + return 0; +} + static int ptrace_attach(struct task_struct *task, long request, unsigned long addr, unsigned long flags) @@ -375,8 +395,16 @@ static int ptrace_attach(struct task_str if (seize) { if (addr != 0) goto out; + /* + * This duplicates the check in check_ptrace_options() because + * ptrace_attach() and ptrace_setoptions() have historically + * used different error codes for unknown ptrace options. + */ if (flags & ~(unsigned long)PTRACE_O_MASK) goto out; + retval = check_ptrace_options(flags); + if (retval) + return retval; flags = PT_PTRACED | PT_SEIZED | (flags << PT_OPT_FLAG_SHIFT); } else { flags = PT_PTRACED; @@ -649,22 +677,11 @@ int ptrace_writedata(struct task_struct static int ptrace_setoptions(struct task_struct *child, unsigned long data) { unsigned flags; + int ret;
- if (data & ~(unsigned long)PTRACE_O_MASK) - return -EINVAL; - - if (unlikely(data & PTRACE_O_SUSPEND_SECCOMP)) { - if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) || - !IS_ENABLED(CONFIG_SECCOMP)) - return -EINVAL; - - if (!capable(CAP_SYS_ADMIN)) - return -EPERM; - - if (seccomp_mode(¤t->seccomp) != SECCOMP_MODE_DISABLED || - current->ptrace & PT_SUSPEND_SECCOMP) - return -EPERM; - } + ret = check_ptrace_options(data); + if (ret) + return ret;
/* Avoid intermediate state when all opts are cleared */ flags = child->ptrace;