[PATCH 4.1 13/86] powerpc/rtas: Validate rtas.entry before calling enter_rtas()

From: Greg Kroah-Hartman
Date: Fri Nov 06 2015 - 15:26:41 EST

4.1-stable review patch. If anyone has any objections, please let me know.


From: Vasant Hegde <hegdevasant@xxxxxxxxxxxxxxxxxx>

commit 8832317f662c06f5c06e638f57bfe89a71c9b266 upstream.

Currently we do not validate rtas.entry before calling enter_rtas(). This
leads to a kernel oops when user space calls rtas system call on a powernv
platform (see below). This patch adds code to validate rtas.entry before
making enter_rtas() call.

Oops: Exception in kernel mode, sig: 4 [#1]
task: c000000004294b80 ti: c0000007e1a78000 task.ti: c0000007e1a78000
NIP: 0000000000000000 LR: 0000000000009c14 CTR: c000000000423140
REGS: c0000007e1a7b920 TRAP: 0e40 Not tainted (3.18.17-340.el7_1.pkvm3_1_0.2400.1.ppc64le)
MSR: 1000000000081000 <HV,ME> CR: 00000000 XER: 00000000
CFAR: c000000000009c0c SOFTE: 0
NIP [0000000000000000] (null)
LR [0000000000009c14] 0x9c14
Call Trace:
[c0000007e1a7bba0] [c00000000041a7f4] avc_has_perm_noaudit+0x54/0x110 (unreliable)
[c0000007e1a7bd80] [c00000000002ddc0] ppc_rtas+0x150/0x2d0
[c0000007e1a7be30] [c000000000009358] syscall_exit+0x0/0x98

Fixes: 55190f88789a ("powerpc: Add skeleton PowerNV platform")
Reported-by: NAGESWARA R. SASTRY <nasastry@xxxxxxxxxx>
Signed-off-by: Vasant Hegde <hegdevasant@xxxxxxxxxxxxxxxxxx>
[mpe: Reword change log, trim oops, and add stable + fixes]
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/powerpc/kernel/rtas.c | 3 +++
1 file changed, 3 insertions(+)

--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -1041,6 +1041,9 @@ asmlinkage int ppc_rtas(struct rtas_args
if (!capable(CAP_SYS_ADMIN))
return -EPERM;

+ if (!rtas.entry)
+ return -EINVAL;
if (copy_from_user(&args, uargs, 3 * sizeof(u32)) != 0)
return -EFAULT;

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