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Subject[PATCH] SGI UV: uv_ptc_proc_write security hole
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From: Cliff Wickman <cpw@sgi.com>

Someone could write 0 bytes to /proc/sgi_uv/ptc_statistics,
causing
optstr[count - 1] = '\0';
to write to who-knows-where.

(Andi Kleen noticed this need from a patch I sent for
similar code in the ia64 world (sn2_ptc_proc_write()).)

(count less than zero is not possible here, as count is unsigned)

Diffed against 2.6.26-rc6

Signed-off-by: Cliff Wickman <cpw@sgi.com>
---
arch/x86/kernel/tlb_uv.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux/arch/x86/kernel/tlb_uv.c
===================================================================
--- linux.orig/arch/x86/kernel/tlb_uv.c
+++ linux/arch/x86/kernel/tlb_uv.c
@@ -492,7 +492,7 @@ static ssize_t uv_ptc_proc_write(struct
long newmode;
char optstr[64];

- if (count > 64)
+ if (count == 0 || count > sizeof(optstr))
return -EINVAL;
if (copy_from_user(optstr, user, count))
return -EFAULT;

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