[PATCH OLK-6.6 057/112] mm: add a NO_INHERIT flag to the PR_SET_MDWE prctl

From: Florent Revest revest@chromium.org

stable inclusion from stable-v6.6.4 commit 2b00d1fd9a40eede0dd38265f839026a4bb2b4b1 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I8N1WC

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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[ Upstream commit 24e41bf8a6b424c76c5902fb999e9eca61bdf83d ]

This extends the current PR_SET_MDWE prctl arg with a bit to indicate that the process doesn't want MDWE protection to propagate to children.

To implement this no-inherit mode, the tag in current->mm->flags must be absent from MMF_INIT_MASK. This means that the encoding for "MDWE but without inherit" is different in the prctl than in the mm flags. This leads to a bit of bit-mangling in the prctl implementation.

Link: https://lkml.kernel.org/r/20230828150858.393570-6-revest@chromium.org Signed-off-by: Florent Revest revest@chromium.org Reviewed-by: Kees Cook keescook@chromium.org Reviewed-by: Catalin Marinas catalin.marinas@arm.com Cc: Alexey Izbyshev izbyshev@ispras.ru Cc: Anshuman Khandual anshuman.khandual@arm.com Cc: Ayush Jain ayush.jain3@amd.com Cc: David Hildenbrand david@redhat.com Cc: Greg Thelen gthelen@google.com Cc: Joey Gouly joey.gouly@arm.com Cc: KP Singh kpsingh@kernel.org Cc: Mark Brown broonie@kernel.org Cc: Michal Hocko mhocko@suse.com Cc: Peter Xu peterx@redhat.com Cc: Ryan Roberts ryan.roberts@arm.com Cc: Szabolcs Nagy Szabolcs.Nagy@arm.com Cc: Topi Miettinen toiwoton@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Stable-dep-of: 793838138c15 ("prctl: Disable prctl(PR_SET_MDWE) on parisc") Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- include/linux/sched/coredump.h | 10 ++++++++++ include/uapi/linux/prctl.h | 1 + kernel/fork.c | 2 +- kernel/sys.c | 32 ++++++++++++++++++++++++++------ tools/include/uapi/linux/prctl.h | 1 + 5 files changed, 39 insertions(+), 7 deletions(-)

diff --git a/include/linux/sched/coredump.h b/include/linux/sched/coredump.h index 0ee96ea7a0e9..1b37fa8fc723 100644 --- a/include/linux/sched/coredump.h +++ b/include/linux/sched/coredump.h @@ -91,4 +91,14 @@ static inline int get_dumpable(struct mm_struct *mm) MMF_DISABLE_THP_MASK | MMF_HAS_MDWE_MASK)

#define MMF_VM_MERGE_ANY 29 +#define MMF_HAS_MDWE_NO_INHERIT 30 + +static inline unsigned long mmf_init_flags(unsigned long flags) +{ + if (flags & (1UL << MMF_HAS_MDWE_NO_INHERIT)) + flags &= ~((1UL << MMF_HAS_MDWE) | + (1UL << MMF_HAS_MDWE_NO_INHERIT)); + return flags & MMF_INIT_MASK; +} + #endif /* _LINUX_SCHED_COREDUMP_H */ diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 9a85c69782bd..370ed14b1ae0 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -284,6 +284,7 @@ struct prctl_mm_map { /* Memory deny write / execute */ #define PR_SET_MDWE 65 # define PR_MDWE_REFUSE_EXEC_GAIN (1UL << 0) +# define PR_MDWE_NO_INHERIT (1UL << 1)

#define PR_GET_MDWE 66

diff --git a/kernel/fork.c b/kernel/fork.c index 3b6d20dfb9a8..177ce7438db6 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1288,7 +1288,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, hugetlb_count_init(mm);

if (current->mm) { - mm->flags = current->mm->flags & MMF_INIT_MASK; + mm->flags = mmf_init_flags(current->mm->flags); mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; } else { mm->flags = default_dump_filter; diff --git a/kernel/sys.c b/kernel/sys.c index 2410e3999ebe..4a8073c1b255 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2368,19 +2368,41 @@ static int prctl_set_vma(unsigned long opt, unsigned long start, } #endif /* CONFIG_ANON_VMA_NAME */

+static inline unsigned long get_current_mdwe(void) +{ + unsigned long ret = 0; + + if (test_bit(MMF_HAS_MDWE, &current->mm->flags)) + ret |= PR_MDWE_REFUSE_EXEC_GAIN; + if (test_bit(MMF_HAS_MDWE_NO_INHERIT, &current->mm->flags)) + ret |= PR_MDWE_NO_INHERIT; + + return ret; +} + static inline int prctl_set_mdwe(unsigned long bits, unsigned long arg3, unsigned long arg4, unsigned long arg5) { + unsigned long current_bits; + if (arg3 || arg4 || arg5) return -EINVAL;

- if (bits & ~(PR_MDWE_REFUSE_EXEC_GAIN)) + if (bits & ~(PR_MDWE_REFUSE_EXEC_GAIN | PR_MDWE_NO_INHERIT)) + return -EINVAL; + + /* NO_INHERIT only makes sense with REFUSE_EXEC_GAIN */ + if (bits & PR_MDWE_NO_INHERIT && !(bits & PR_MDWE_REFUSE_EXEC_GAIN)) return -EINVAL;

+ current_bits = get_current_mdwe(); + if (current_bits && current_bits != bits) + return -EPERM; /* Cannot unset the flags */ + + if (bits & PR_MDWE_NO_INHERIT) + set_bit(MMF_HAS_MDWE_NO_INHERIT, &current->mm->flags); if (bits & PR_MDWE_REFUSE_EXEC_GAIN) set_bit(MMF_HAS_MDWE, &current->mm->flags); - else if (test_bit(MMF_HAS_MDWE, &current->mm->flags)) - return -EPERM; /* Cannot unset the flag */

return 0; } @@ -2390,9 +2412,7 @@ static inline int prctl_get_mdwe(unsigned long arg2, unsigned long arg3, { if (arg2 || arg3 || arg4 || arg5) return -EINVAL; - - return test_bit(MMF_HAS_MDWE, &current->mm->flags) ? - PR_MDWE_REFUSE_EXEC_GAIN : 0; + return get_current_mdwe(); }

static int prctl_get_auxv(void __user *addr, unsigned long len) diff --git a/tools/include/uapi/linux/prctl.h b/tools/include/uapi/linux/prctl.h index 9a85c69782bd..370ed14b1ae0 100644 --- a/tools/include/uapi/linux/prctl.h +++ b/tools/include/uapi/linux/prctl.h @@ -284,6 +284,7 @@ struct prctl_mm_map { /* Memory deny write / execute */ #define PR_SET_MDWE 65 # define PR_MDWE_REFUSE_EXEC_GAIN (1UL << 0) +# define PR_MDWE_NO_INHERIT (1UL << 1)

#define PR_GET_MDWE 66