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Subject[ 59/85] amd64_edac:__amd64_set_scrub_rate(): avoid overindexing scrubrates[]
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3.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrew Morton <akpm@linux-foundation.org>

commit 168bfeef7bba3f9784f7540b053e4ac72b769ce9 upstream.

If none of the elements in scrubrates[] matches, this loop will cause
__amd64_set_scrub_rate() to incorrectly use the n+1th element.

As the function is designed to use the final scrubrates[] element in the
case of no match, we can fix this bug by simply terminating the array
search at the n-1th element.

Boris: this code is fragile anyway, see here why:
http://marc.info/?l=linux-kernel&m=135102834131236&w=2

It will be rewritten more robustly soonish.

Reported-by: Denis Kirjanov <kirjanov@gmail.com>
Cc: Doug Thompson <dougthompson@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/edac/amd64_edac.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)

--- a/drivers/edac/amd64_edac.c
+++ b/drivers/edac/amd64_edac.c
@@ -170,8 +170,11 @@ static int __amd64_set_scrub_rate(struct
* memory controller and apply to register. Search for the first
* bandwidth entry that is greater or equal than the setting requested
* and program that. If at last entry, turn off DRAM scrubbing.
+ *
+ * If no suitable bandwidth is found, turn off DRAM scrubbing entirely
+ * by falling back to the last element in scrubrates[].
*/
- for (i = 0; i < ARRAY_SIZE(scrubrates); i++) {
+ for (i = 0; i < ARRAY_SIZE(scrubrates) - 1; i++) {
/*
* skip scrub rates which aren't recommended
* (see F10 BKDG, F3x58)
@@ -181,12 +184,6 @@ static int __amd64_set_scrub_rate(struct

if (scrubrates[i].bandwidth <= new_bw)
break;
-
- /*
- * if no suitable bandwidth found, turn off DRAM scrubbing
- * entirely by falling back to the last element in the
- * scrubrates array.
- */
}

scrubval = scrubrates[i].scrubval;



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