6.4-stable review patch. If anyone has any objections, please let me know.
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From: Jeff Xu jeffxu@google.com
[ Upstream commit 72de259130229412ca49871e70ffaf17dc9fba98 ]
Patch series "mm/memfd: fix sysctl MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED", v2.
When sysctl vm.memfd_noexec is 2 (MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED), memfd_create(.., MFD_EXEC) should fail.
This complies with how MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED is defined - "memfd_create() without MFD_NOEXEC_SEAL will be rejected"
Thanks to Dominique Martinet asmadeus@codewreck.org who reported the bug. see [1] for context.
[1] https://lore.kernel.org/linux-mm/CABi2SkXUX_QqTQ10Yx9bBUGpN1wByOi_=gZU6WEy5a...
This patch (of 2):
When vm.memfd_noexec is 2 (MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED), memfd_create(.., MFD_EXEC) should fail.
This complies with how MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED is defined - "memfd_create() without MFD_NOEXEC_SEAL will be rejected"
Link: https://lkml.kernel.org/r/20230705063315.3680666-1-jeffxu@google.com Link: https://lkml.kernel.org/r/20230705063315.3680666-2-jeffxu@google.com Fixes: 105ff5339f49 ("mm/memfd: add MFD_NOEXEC_SEAL and MFD_EXEC") Reported-by: Dominique Martinet asmadeus@codewreck.org Closes: https://lore.kernel.org/linux-mm/CABi2SkXUX_QqTQ10Yx9bBUGpN1wByOi_=gZU6WEy5a... Reported-by: kernel test robot lkp@intel.com Closes: https://lore.kernel.org/oe-kbuild-all/202306301351.kkbSegQW-lkp@intel.com/ Signed-off-by: Jeff Xu jeffxu@google.com Cc: Daniel Verkamp dverkamp@chromium.org Cc: Dmitry Torokhov dmitry.torokhov@gmail.com Cc: Hugh Dickins hughd@google.com Cc: Jann Horn jannh@google.com Cc: Jorge Lucangeli Obes jorgelo@chromium.org Cc: Kees Cook keescook@chromium.org Cc: Shuah Khan skhan@linuxfoundation.org Cc: Mike Kravetz mike.kravetz@oracle.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Stable-dep-of: 202e14222fad ("memfd: do not -EACCES old memfd_create() users with vm.memfd_noexec=2") Signed-off-by: Sasha Levin sashal@kernel.org --- mm/memfd.c | 57 +++++++++++++++++++++++++++++++----------------------- 1 file changed, 33 insertions(+), 24 deletions(-)
diff --git a/mm/memfd.c b/mm/memfd.c index e763e76f11064..0bdbd2335af75 100644 --- a/mm/memfd.c +++ b/mm/memfd.c @@ -268,6 +268,36 @@ long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | MFD_NOEXEC_SEAL | MFD_EXEC)
+static int check_sysctl_memfd_noexec(unsigned int *flags) +{ +#ifdef CONFIG_SYSCTL + char comm[TASK_COMM_LEN]; + int sysctl = MEMFD_NOEXEC_SCOPE_EXEC; + struct pid_namespace *ns; + + ns = task_active_pid_ns(current); + if (ns) + sysctl = ns->memfd_noexec_scope; + + if (!(*flags & (MFD_EXEC | MFD_NOEXEC_SEAL))) { + if (sysctl == MEMFD_NOEXEC_SCOPE_NOEXEC_SEAL) + *flags |= MFD_NOEXEC_SEAL; + else + *flags |= MFD_EXEC; + } + + if (*flags & MFD_EXEC && sysctl >= MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED) { + pr_warn_once( + "memfd_create(): MFD_NOEXEC_SEAL is enforced, pid=%d '%s'\n", + task_pid_nr(current), get_task_comm(comm, current)); + + return -EACCES; + } +#endif + + return 0; +} + SYSCALL_DEFINE2(memfd_create, const char __user *, uname, unsigned int, flags) @@ -294,35 +324,14 @@ SYSCALL_DEFINE2(memfd_create, return -EINVAL;
if (!(flags & (MFD_EXEC | MFD_NOEXEC_SEAL))) { -#ifdef CONFIG_SYSCTL - int sysctl = MEMFD_NOEXEC_SCOPE_EXEC; - struct pid_namespace *ns; - - ns = task_active_pid_ns(current); - if (ns) - sysctl = ns->memfd_noexec_scope; - - switch (sysctl) { - case MEMFD_NOEXEC_SCOPE_EXEC: - flags |= MFD_EXEC; - break; - case MEMFD_NOEXEC_SCOPE_NOEXEC_SEAL: - flags |= MFD_NOEXEC_SEAL; - break; - default: - pr_warn_once( - "memfd_create(): MFD_NOEXEC_SEAL is enforced, pid=%d '%s'\n", - task_pid_nr(current), get_task_comm(comm, current)); - return -EINVAL; - } -#else - flags |= MFD_EXEC; -#endif pr_warn_once( "memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL, pid=%d '%s'\n", task_pid_nr(current), get_task_comm(comm, current)); }
+ if (check_sysctl_memfd_noexec(&flags) < 0) + return -EACCES; + /* length includes terminating zero */ len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1); if (len <= 0)