6.14-stable review patch. If anyone has any objections, please let me know.
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From: Andre Przywara andre.przywara@arm.com
[ Upstream commit 14c8a418159e541d70dbf8fc71225d1623beaf0f ]
A KASAN enabled kernel reports an out-of-bounds access when handling the nvmem cell in the sun50i cpufreq driver: ================================================================== BUG: KASAN: slab-out-of-bounds in sun50i_cpufreq_nvmem_probe+0x180/0x3d4 Read of size 4 at addr ffff000006bf31e0 by task kworker/u16:1/38
This is because the DT specifies the nvmem cell as covering only two bytes, but we use a u32 pointer to read the value. DTs for other SoCs indeed specify 4 bytes, so we cannot just shorten the variable to a u16.
Fortunately nvmem_cell_read() allows to return the length of the nvmem cell, in bytes, so we can use that information to only access the valid portion of the data. To cover multiple cell sizes, use memcpy() to copy the information into a zeroed u32 buffer, then also make sure we always read the data in little endian fashion, as this is how the data is stored in the SID efuses.
Fixes: 6cc4bcceff9a ("cpufreq: sun50i: Refactor speed bin decoding") Reported-by: Jernej Skrabec jernej.skrabec@gmail.com Signed-off-by: Andre Przywara andre.przywara@arm.com Reviewed-by: Jernej Škrabec jernej.skrabec@gmail.com Signed-off-by: Viresh Kumar viresh.kumar@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/cpufreq/sun50i-cpufreq-nvmem.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/drivers/cpufreq/sun50i-cpufreq-nvmem.c b/drivers/cpufreq/sun50i-cpufreq-nvmem.c index 47d6840b34899..744312a44279c 100644 --- a/drivers/cpufreq/sun50i-cpufreq-nvmem.c +++ b/drivers/cpufreq/sun50i-cpufreq-nvmem.c @@ -194,7 +194,9 @@ static int sun50i_cpufreq_get_efuse(void) struct nvmem_cell *speedbin_nvmem; const struct of_device_id *match; struct device *cpu_dev; - u32 *speedbin; + void *speedbin_ptr; + u32 speedbin = 0; + size_t len; int ret;
cpu_dev = get_cpu_device(0); @@ -217,14 +219,18 @@ static int sun50i_cpufreq_get_efuse(void) return dev_err_probe(cpu_dev, PTR_ERR(speedbin_nvmem), "Could not get nvmem cell\n");
- speedbin = nvmem_cell_read(speedbin_nvmem, NULL); + speedbin_ptr = nvmem_cell_read(speedbin_nvmem, &len); nvmem_cell_put(speedbin_nvmem); - if (IS_ERR(speedbin)) - return PTR_ERR(speedbin); + if (IS_ERR(speedbin_ptr)) + return PTR_ERR(speedbin_ptr);
- ret = opp_data->efuse_xlate(*speedbin); + if (len <= 4) + memcpy(&speedbin, speedbin_ptr, len); + speedbin = le32_to_cpu(speedbin);
- kfree(speedbin); + ret = opp_data->efuse_xlate(speedbin); + + kfree(speedbin_ptr);
return ret; };