| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.0 036/105] drivers/base: cacheinfo: handle absence of caches | Date | Fri, 19 Jun 2015 13:35:26 -0700 |
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4.0-stable review patch. If anyone has any objections, please let me know.
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From: Sudeep Holla <sudeep.holla@arm.com>
commit 3370e13aa463adb84488ebf0e599e3dc0024315b upstream.
On some simulators like GEM5, caches may not be simulated. In those cases, the cache levels and leaves will be zero and will result in following exception:
Unable to handle kernel NULL pointer dereference at virtual address 0040 pgd = ffffffc0008fa000 [00000040] *pgd=00000009f6807003, *pud=00000009f6807003, *pmd=00000009f6808003, *pte=006000002c010707 Internal error: Oops: 96000005 [#1] PREEMPT SMP Modules linked in: CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.1.0-rc5 #198 task: ffffffc9768a0000 ti: ffffffc9768a8000 task.ti: ffffffc9768a8000 PC is at detect_cache_attributes+0x98/0x2c8 LR is at detect_cache_attributes+0x88/0x2c8
kcalloc(0) returns a special value ZERO_SIZE_PTR which is non-NULL value but results in fault only on any attempt to dereferencing it. So checking for the non-NULL pointer will not suffice.
This patch checks for non-zero cache leaf nodes and returns error if there are no cache leaves in detect_cache_attributes.
Cc: Will Deacon <will.deacon@arm.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reported-by: William Wang <william.wang@arm.com> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/base/cacheinfo.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/base/cacheinfo.c +++ b/drivers/base/cacheinfo.c @@ -179,7 +179,7 @@ static int detect_cache_attributes(unsig { int ret; - if (init_cache_level(cpu)) + if (init_cache_level(cpu) || !cache_leaves(cpu)) return -ENOENT; per_cpu_cacheinfo(cpu) = kcalloc(cache_leaves(cpu),
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