score: fix off-by-one index into syscall table

If the provided system call number is equal to __NR_syscalls, the
current check will pass and a function pointer just after the system
call table may be called, since sys_call_table is an array with total
size __NR_syscalls.

Whether or not this is a security bug depends on what the compiler puts
immediately after the system call table.  It's likely that this won't do
anything bad because there is an additional NULL check on the syscall
entry, but if there happens to be a non-NULL value immediately after the
system call table, this may result in local privilege escalation.

Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: <stable@vger.kernel.org>
Cc: Chen Liqin <liqin.chen@sunplusct.com>
Cc: Lennox Wu <lennox.wu@gmail.com>
Cc: Eugene Teo <eugeneteo@kernel.sg>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/score/kernel/entry.S b/arch/score/kernel/entry.S
index 577abba3fac6..83bb96079c43 100644
--- a/arch/score/kernel/entry.S
+++ b/arch/score/kernel/entry.S
@@ -408,7 +408,7 @@ ENTRY(handle_sys)
         sw      r9, [r0, PT_EPC]
 
         cmpi.c  r27, __NR_syscalls      # check syscall number
-        bgtu    illegal_syscall
+        bgeu    illegal_syscall
 
         slli    r8, r27, 2              # get syscall routine
         la      r11, sys_call_table