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author | Eric W. Biederman <ebiederm@xmission.com> | 2016-10-13 21:23:16 -0500 |
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committer | Eric W. Biederman <ebiederm@xmission.com> | 2016-11-22 11:49:48 -0600 |
commit | bfedb589252c01fa505ac9f6f2a3d5d68d707ef4 (patch) | |
tree | f4a3b443cc77423d0550c9a21d82175246a0f3d5 /mm/init-mm.c | |
parent | 9c763584b7c8911106bb77af7e648bef09af9d80 (diff) | |
download | linux-bfedb589252c01fa505ac9f6f2a3d5d68d707ef4.tar.gz |
mm: Add a user_ns owner to mm_struct and fix ptrace permission checks
During exec dumpable is cleared if the file that is being executed is not readable by the user executing the file. A bug in ptrace_may_access allows reading the file if the executable happens to enter into a subordinate user namespace (aka clone(CLONE_NEWUSER), unshare(CLONE_NEWUSER), or setns(fd, CLONE_NEWUSER). This problem is fixed with only necessary userspace breakage by adding a user namespace owner to mm_struct, captured at the time of exec, so it is clear in which user namespace CAP_SYS_PTRACE must be present in to be able to safely give read permission to the executable. The function ptrace_may_access is modified to verify that the ptracer has CAP_SYS_ADMIN in task->mm->user_ns instead of task->cred->user_ns. This ensures that if the task changes it's cred into a subordinate user namespace it does not become ptraceable. The function ptrace_attach is modified to only set PT_PTRACE_CAP when CAP_SYS_PTRACE is held over task->mm->user_ns. The intent of PT_PTRACE_CAP is to be a flag to note that whatever permission changes the task might go through the tracer has sufficient permissions for it not to be an issue. task->cred->user_ns is always the same as or descendent of mm->user_ns. Which guarantees that having CAP_SYS_PTRACE over mm->user_ns is the worst case for the tasks credentials. To prevent regressions mm->dumpable and mm->user_ns are not considered when a task has no mm. As simply failing ptrace_may_attach causes regressions in privileged applications attempting to read things such as /proc/<pid>/stat Cc: stable@vger.kernel.org Acked-by: Kees Cook <keescook@chromium.org> Tested-by: Cyrill Gorcunov <gorcunov@openvz.org> Fixes: 8409cca70561 ("userns: allow ptrace from non-init user namespaces") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'mm/init-mm.c')
-rw-r--r-- | mm/init-mm.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/mm/init-mm.c b/mm/init-mm.c index a56a851908d2..975e49f00f34 100644 --- a/mm/init-mm.c +++ b/mm/init-mm.c @@ -6,6 +6,7 @@ #include <linux/cpumask.h> #include <linux/atomic.h> +#include <linux/user_namespace.h> #include <asm/pgtable.h> #include <asm/mmu.h> @@ -21,5 +22,6 @@ struct mm_struct init_mm = { .mmap_sem = __RWSEM_INITIALIZER(init_mm.mmap_sem), .page_table_lock = __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock), .mmlist = LIST_HEAD_INIT(init_mm.mmlist), + .user_ns = &init_user_ns, INIT_MM_CONTEXT(init_mm) }; |