Patch "MIPS: scache: Fix scache init with invalid line size." has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

MIPS: scache: Fix scache init with invalid line size.

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mips-scache-fix-scache-init-with-invalid-line-size.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Govindraj Raja <[email protected]>
Date: Mon, 29 Feb 2016 11:41:20 +0000
Subject: MIPS: scache: Fix scache init with invalid line size.

From: Govindraj Raja <[email protected]>

commit 56fa81fc9a5445938f3aa2e63d15ab63dc938ad6 upstream.

In current scache init cache line_size is determined from cpu config register, however if there there no scache then mips_sc_probe_cm3 function populates a invalid line_size of 2.

The invalid line_size can cause a NULL pointer deference during r4k_dma_cache_inv as r4k_blast_scache is populated based on line_size. Scache line_size of 2 is invalid option in r4k_blast_scache_setup.

This issue was faced during a MIPS I6400 based virtual platform bring up where scache was not available in virtual platform model.

Patchwork: https://patchwork.linux-mips.org/patch/12710/

---
 arch/mips/mm/sc-mips.c |   13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

@@ -164,11 +164,13 @@ static int __init mips_sc_probe_cm3(void
 
 	sets = cfg & CM_GCR_L2_CONFIG_SET_SIZE_MSK;
 	sets >>= CM_GCR_L2_CONFIG_SET_SIZE_SHF;
-	c->scache.sets = 64 << sets;
+	if (sets)
+		c->scache.sets = 64 << sets;
 
 	line_sz = cfg & CM_GCR_L2_CONFIG_LINE_SIZE_MSK;
 	line_sz >>= CM_GCR_L2_CONFIG_LINE_SIZE_SHF;
-	c->scache.linesz = 2 << line_sz;
+	if (line_sz)
+		c->scache.linesz = 2 << line_sz;
 
 	assoc = cfg & CM_GCR_L2_CONFIG_ASSOC_MSK;
 	assoc >>= CM_GCR_L2_CONFIG_ASSOC_SHF;

@@ -176,9 +178,12 @@ static int __init mips_sc_probe_cm3(void
 	c->scache.waysize = c->scache.sets * c->scache.linesz;
 	c->scache.waybit = __ffs(c->scache.waysize);
 
-	c->scache.flags &= ~MIPS_CACHE_NOT_PRESENT;
+	if (c->scache.linesz) {
+		c->scache.flags &= ~MIPS_CACHE_NOT_PRESENT;
+		return 1;
+	}
 
-	return 1;
+	return 0;
 }
 
 void __weak platform_early_l2_init(void)

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/mips-scache-fix-scache-init-with-invalid-line-size.patch