lsm: new security_file_ioctl_compat() hook

Some ioctl commands do not require ioctl permission, but are routed to
other permissions such as FILE_GETATTR or FILE_SETATTR. This routing is
done by comparing the ioctl cmd to a set of 64-bit flags (FS_IOC_*).

However, if a 32-bit process is running on a 64-bit kernel, it emits
32-bit flags (FS_IOC32_*) for certain ioctl operations. These flags are
being checked erroneously, which leads to these ioctl operations being
routed to the ioctl permission, rather than the correct file
permissions.

This was also noted in a RED-PEN finding from a while back -
"/* RED-PEN how should LSM module know it's handling 32bit? */".

This patch introduces a new hook, security_file_ioctl_compat(), that is
called from the compat ioctl syscall. All current LSMs have been changed
to support this hook.

Reviewing the three places where we are currently using
security_file_ioctl(), it appears that only SELinux needs a dedicated
compat change; TOMOYO and SMACK appear to be functional without any
change.

Cc: stable@vger.kernel.org
Fixes: 0b24dcb7f2f7 ("Revert "selinux: simplify ioctl checking"")
Signed-off-by: Alfred Piccioni <alpic@google.com>
Reviewed-by: Stephen Smalley <stephen.smalley.work@gmail.com>
[PM: subject tweak, line length fixes, and alignment corrections]
Signed-off-by: Paul Moore <paul@paul-moore.com>

diff --git a/fs/ioctl.c b/fs/ioctl.c
index f5fd99d6b0d4ed981811797e35f254c98cd70e25..76cf22ac97d76256104a6dbc4f819247168ce769 100644 (file)
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -920,8 +920,7 @@ COMPAT_SYSCALL_DEFINE3(ioctl, unsigned int, fd, unsigned int, cmd,
        if (!f.file)
                return -EBADF;
 
-       /* RED-PEN how should LSM module know it's handling 32bit? */
-       error = security_file_ioctl(f.file, cmd, arg);
+       error = security_file_ioctl_compat(f.file, cmd, arg);
        if (error)
                goto out;
 

diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index c925a0d26edfe87b6168386eeea3672ba5c8b60a..185924c5637876a153957a3a206fe907dcc784a5 100644 (file)
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -171,6 +171,8 @@ LSM_HOOK(int, 0, file_alloc_security, struct file *file)
 LSM_HOOK(void, LSM_RET_VOID, file_free_security, struct file *file)
 LSM_HOOK(int, 0, file_ioctl, struct file *file, unsigned int cmd,
         unsigned long arg)
+LSM_HOOK(int, 0, file_ioctl_compat, struct file *file, unsigned int cmd,
+        unsigned long arg)
 LSM_HOOK(int, 0, mmap_addr, unsigned long addr)
 LSM_HOOK(int, 0, mmap_file, struct file *file, unsigned long reqprot,
         unsigned long prot, unsigned long flags)

diff --git a/include/linux/security.h b/include/linux/security.h
index 750130a7b9dd2ffb8248914b53c6a2a5d0774cd1..d0eb20f90b264a3fdf96bfc60b28e2091638edd8 100644 (file)
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -394,6 +394,8 @@ int security_file_permission(struct file *file, int mask);
 int security_file_alloc(struct file *file);
 void security_file_free(struct file *file);
 int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
+int security_file_ioctl_compat(struct file *file, unsigned int cmd,
+                              unsigned long arg);
 int security_mmap_file(struct file *file, unsigned long prot,
                        unsigned long flags);
 int security_mmap_addr(unsigned long addr);
@@ -1002,6 +1004,13 @@ static inline int security_file_ioctl(struct file *file, unsigned int cmd,
        return 0;
 }
 
+static inline int security_file_ioctl_compat(struct file *file,
+                                            unsigned int cmd,
+                                            unsigned long arg)
+{
+       return 0;
+}
+
 static inline int security_mmap_file(struct file *file, unsigned long prot,
                                     unsigned long flags)
 {

diff --git a/security/security.c b/security/security.c
index d7b15ea67c3f51b23bc1d1ec3b35d2d14d80ac21..69148dfc90cd2fbecd0935fe20f2e2888f646e5e 100644 (file)
--- a/security/security.c
+++ b/security/security.c
@@ -2732,6 +2732,24 @@ int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 }
 EXPORT_SYMBOL_GPL(security_file_ioctl);
 
+/**
+ * security_file_ioctl_compat() - Check if an ioctl is allowed in compat mode
+ * @file: associated file
+ * @cmd: ioctl cmd
+ * @arg: ioctl arguments
+ *
+ * Compat version of security_file_ioctl() that correctly handles 32-bit
+ * processes running on 64-bit kernels.
+ *
+ * Return: Returns 0 if permission is granted.
+ */
+int security_file_ioctl_compat(struct file *file, unsigned int cmd,
+                              unsigned long arg)
+{
+       return call_int_hook(file_ioctl_compat, 0, file, cmd, arg);
+}
+EXPORT_SYMBOL_GPL(security_file_ioctl_compat);
+
 static inline unsigned long mmap_prot(struct file *file, unsigned long prot)
 {
        /*

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index b340425ccfae1c82bd4fbd7d9eb9985d558274f0..17954044111533adaf20773ebfb8f1a68d6f077f 100644 (file)
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3732,6 +3732,33 @@ static int selinux_file_ioctl(struct file *file, unsigned int cmd,
        return error;
 }
 
+static int selinux_file_ioctl_compat(struct file *file, unsigned int cmd,
+                             unsigned long arg)
+{
+       /*
+        * If we are in a 64-bit kernel running 32-bit userspace, we need to
+        * make sure we don't compare 32-bit flags to 64-bit flags.
+        */
+       switch (cmd) {
+       case FS_IOC32_GETFLAGS:
+               cmd = FS_IOC_GETFLAGS;
+               break;
+       case FS_IOC32_SETFLAGS:
+               cmd = FS_IOC_SETFLAGS;
+               break;
+       case FS_IOC32_GETVERSION:
+               cmd = FS_IOC_GETVERSION;
+               break;
+       case FS_IOC32_SETVERSION:
+               cmd = FS_IOC_SETVERSION;
+               break;
+       default:
+               break;
+       }
+
+       return selinux_file_ioctl(file, cmd, arg);
+}
+
 static int default_noexec __ro_after_init;
 
 static int file_map_prot_check(struct file *file, unsigned long prot, int shared)
@@ -7122,6 +7149,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
        LSM_HOOK_INIT(file_permission, selinux_file_permission),
        LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security),
        LSM_HOOK_INIT(file_ioctl, selinux_file_ioctl),
+       LSM_HOOK_INIT(file_ioctl_compat, selinux_file_ioctl_compat),
        LSM_HOOK_INIT(mmap_file, selinux_mmap_file),
        LSM_HOOK_INIT(mmap_addr, selinux_mmap_addr),
        LSM_HOOK_INIT(file_mprotect, selinux_file_mprotect),

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 53336d7daa93324cc72d66c928e3a34fc6edfdbb..c126f6a16de4fbd0d3c05ba93529c50e23093263 100644 (file)
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -5051,6 +5051,7 @@ static struct security_hook_list smack_hooks[] __ro_after_init = {
 
        LSM_HOOK_INIT(file_alloc_security, smack_file_alloc_security),
        LSM_HOOK_INIT(file_ioctl, smack_file_ioctl),
+       LSM_HOOK_INIT(file_ioctl_compat, smack_file_ioctl),
        LSM_HOOK_INIT(file_lock, smack_file_lock),
        LSM_HOOK_INIT(file_fcntl, smack_file_fcntl),
        LSM_HOOK_INIT(mmap_file, smack_mmap_file),

diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
index e10491f155a5cd3707f137dd6979c2a25fecaad5..3c3af149bf1c12a94c318d188984ab4bda4a2edc 100644 (file)
--- a/security/tomoyo/tomoyo.c
+++ b/security/tomoyo/tomoyo.c
@@ -574,6 +574,7 @@ static struct security_hook_list tomoyo_hooks[] __ro_after_init = {
        LSM_HOOK_INIT(path_rename, tomoyo_path_rename),
        LSM_HOOK_INIT(inode_getattr, tomoyo_inode_getattr),
        LSM_HOOK_INIT(file_ioctl, tomoyo_file_ioctl),
+       LSM_HOOK_INIT(file_ioctl_compat, tomoyo_file_ioctl),
        LSM_HOOK_INIT(path_chmod, tomoyo_path_chmod),
        LSM_HOOK_INIT(path_chown, tomoyo_path_chown),
        LSM_HOOK_INIT(path_chroot, tomoyo_path_chroot),