Re: [PATCH] sysctl: Delete the code of sys_sysctl

[Xiaoming Ni]

On 2020/6/9 23:40, Kees Cook wrote:
> On Tue, Jun 09, 2020 at 02:20:05PM +0800, Xiaoming Ni wrote:
> > Since the commit 61a47c1ad3a4dc ("sysctl: Remove the sysctl system call"),
> > sys_sysctl has lost its actual role: any input can only return an error.
> >
> > Delete the code and return -ENOSYS directly at the function entry
> >
> > Signed-off-by: Xiaoming Ni <nixiaoming@xxxxxxxxxx>
>
> Looks right to me.
>
> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
>
> Should this be taken a step further and just remove the syscall entirely
> and update the per-arch tables with the ENOSYS hole?
>
> -Kees
Searching for git log, I found a commit record that deleted syscall:
commit f5b94099739722 ("All Arch: remove linkage for sys_nfsservctl 
system call"). Could I use sys_ni_syscall to implement the hole as in 
the example here?
E.g:
diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
index 7b3832d..f36fda6 100644
--- a/arch/arm/tools/syscall.tbl
+++ b/arch/arm/tools/syscall.tbl
@@ -162,7 +162,7 @@
 146    common  writev                  sys_writev
 147    common  getsid                  sys_getsid
 148    common  fdatasync               sys_fdatasync
-149        common  _sysctl                 sys_sysctl
+149  common  _sysctl                 sys_ni_syscall
 150    common  mlock                   sys_mlock
 151    common  munlock                 sys_munlock
 152    common  mlockall                sys_mlockall
diff --git a/arch/arm64/include/asm/unistd32.h 
b/arch/arm64/include/asm/unistd32.h
index f8dafe9..ca41bb7 100644
--- a/arch/arm64/include/asm/unistd32.h
+++ b/arch/arm64/include/asm/unistd32.h
@@ -308,8 +308,8 @@
 __SYSCALL(__NR_getsid, sys_getsid)
 #define __NR_fdatasync 148
 __SYSCALL(__NR_fdatasync, sys_fdatasync)
-#define __NR__sysctl 149
-__SYSCALL(__NR__sysctl, compat_sys_sysctl)
+                 /* 149 was sys_sysctl */
+__SYSCALL(149, sys_ni_syscall)
 #define __NR_mlock 150
 __SYSCALL(__NR_mlock, sys_mlock)
 #define __NR_munlock 151


In this case, I need to modify a lot of code in v2. Can I add 
"Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>" to the v2 patch?

Thanks
Xiaoming Ni