alpha: fix several security issues

Fix several security issues in Alpha-specific syscalls.  Untested, but
mostly trivial.

1. Signedness issue in osf_getdomainname allows copying out-of-bounds
kernel memory to userland.

2. Signedness issue in osf_sysinfo allows copying large amounts of
kernel memory to userland.

3. Typo (?) in osf_getsysinfo bounds minimum instead of maximum copy
size, allowing copying large amounts of kernel memory to userland.

4. Usage of user pointer in osf_wait4 while under KERNEL_DS allows
privilege escalation via writing return value of sys_wait4 to kernel
memory.

Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 4 deletions

diff --git a/arch/alpha/kernel/osf_sys.c b/arch/alpha/kernel/osf_sys.c
index 376f22130791..326f0a2d56e5 100644
--- a/arch/alpha/kernel/osf_sys.c
+++ b/arch/alpha/kernel/osf_sys.c
@@ -409,7 +409,7 @@ SYSCALL_DEFINE2(osf_getdomainname, char __user *, name, int, namelen)
                 return -EFAULT;
 
         len = namelen;
-        if (namelen > 32)
+        if (len > 32)
                 len = 32;
 
         down_read(&uts_sem);
@@ -594,7 +594,7 @@ SYSCALL_DEFINE3(osf_sysinfo, int, command, char __user *, buf, long, count)
         down_read(&uts_sem);
         res = sysinfo_table[offset];
         len = strlen(res)+1;
-        if (len > count)
+        if ((unsigned long)len > (unsigned long)count)
                 len = count;
         if (copy_to_user(buf, res, len))
                 err = -EFAULT;
@@ -649,7 +649,7 @@ SYSCALL_DEFINE5(osf_getsysinfo, unsigned long, op, void __user *, buffer,
                 return 1;
 
         case GSI_GET_HWRPB:
-                if (nbytes < sizeof(*hwrpb))
+                if (nbytes > sizeof(*hwrpb))
                         return -EINVAL;
                 if (copy_to_user(buffer, hwrpb, nbytes) != 0)
                         return -EFAULT;
@@ -1008,6 +1008,7 @@ SYSCALL_DEFINE4(osf_wait4, pid_t, pid, int __user *, ustatus, int, options,
 {
         struct rusage r;
         long ret, err;
+        unsigned int status = 0;
         mm_segment_t old_fs;
 
         if (!ur)
@@ -1016,13 +1017,15 @@ SYSCALL_DEFINE4(osf_wait4, pid_t, pid, int __user *, ustatus, int, options,
         old_fs = get_fs();
                 
         set_fs (KERNEL_DS);
-        ret = sys_wait4(pid, ustatus, options, (struct rusage __user *) &r);
+        ret = sys_wait4(pid, (unsigned int __user *) &status, options,
+                        (struct rusage __user *) &r);
         set_fs (old_fs);
 
         if (!access_ok(VERIFY_WRITE, ur, sizeof(*ur)))
                 return -EFAULT;
 
         err = 0;
+        err |= put_user(status, ustatus);
         err |= __put_user(r.ru_utime.tv_sec, &ur->ru_utime.tv_sec);
         err |= __put_user(r.ru_utime.tv_usec, &ur->ru_utime.tv_usec);
         err |= __put_user(r.ru_stime.tv_sec, &ur->ru_stime.tv_sec);