Patchwork powerpc: Prevent unsigned wrap in htab_dt_scan_page_sizes()

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Submitter roel kluin
Date Oct. 14, 2009, 12:12 p.m.
Message ID <4AD5C01E.8000600@gmail.com>
Download mbox | patch
Permalink /patch/35956/
State Changes Requested
Headers show

Comments

roel kluin - Oct. 14, 2009, 12:12 p.m.
Check to prevent unsigned wrap of size before subtraction.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
---
Is this maybe better or are we certain that size can't wrap?
Paul Mackerras - Oct. 14, 2009, 9:29 p.m.
Roel Kluin writes:

> Check to prevent unsigned wrap of size before subtraction.
> 
> Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
> ---
> Is this maybe better or are we certain that size can't wrap?

Patch looks good, though while you're at it, you could add a space
after the "while".

Acked-by: Paul Mackerras <paulus@samba.org>

Patch

diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 1ade7eb..dd2d263 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -287,7 +287,7 @@  static int __init htab_dt_scan_page_sizes(unsigned long node,
 		DBG("Page sizes from device-tree:\n");
 		size /= 4;
 		cur_cpu_spec->cpu_features &= ~(CPU_FTR_16M_PAGE);
-		while(size > 0) {
+		while(size >= 3) {
 			unsigned int shift = prop[0];
 			unsigned int slbenc = prop[1];
 			unsigned int lpnum = prop[2];
@@ -296,7 +296,7 @@  static int __init htab_dt_scan_page_sizes(unsigned long node,
 			int idx = -1;
 
 			size -= 3; prop += 3;
-			while(size > 0 && lpnum) {
+			while(size >= 2 && lpnum) {
 				if (prop[0] == shift)
 					lpenc = prop[1];
 				prop += 2; size -= 2;