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mm/memfd: sysctl: fix MEMFD_NOEXEC_SCOPE_NOEXEC_ENFORCED

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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_=gZU6WEy5a8MaQY3Jw@mail.gmail.com/T/


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: 105ff5339f ("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_=gZU6WEy5a8MaQY3Jw@mail.gmail.com/T/
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>
This commit is contained in:
Jeff Xu 2023-07-05 06:33:14 +00:00 committed by Andrew Morton
parent 8a144612eb
commit 72de259130
1 changed files with 33 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

57
mm/memfd.c
View File

@ -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)