Re: [PATCH] rsi: Properly initialize data in rsi_sdio_ta_reset
From: Nick Desaulniers <ndesaulniers@google.com>
Date: 2019-05-02 18:18:20
Also in:
linux-wireless, lkml
On Thu, May 2, 2019 at 8:16 AM Nathan Chancellor [off-list ref] wrote:
quoted hunk ↗ jump to hunk
When building with -Wuninitialized, Clang warns: drivers/net/wireless/rsi/rsi_91x_sdio.c:940:43: warning: variable 'data' is uninitialized when used here [-Wuninitialized] put_unaligned_le32(TA_HOLD_THREAD_VALUE, data); ^~~~ drivers/net/wireless/rsi/rsi_91x_sdio.c:930:10: note: initialize the variable 'data' to silence this warning u8 *data; ^ = NULL 1 warning generated. Using Clang's suggestion of initializing data to NULL wouldn't work out because data will be dereferenced by put_unaligned_le32. Use kzalloc to properly initialize data, which matches a couple of other places in this driver. Fixes: e5a1ecc97e5f ("rsi: add firmware loading for 9116 device") Link: https://github.com/ClangBuiltLinux/linux/issues/464 Signed-off-by: Nathan Chancellor <redacted> --- drivers/net/wireless/rsi/rsi_91x_sdio.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-)diff --git a/drivers/net/wireless/rsi/rsi_91x_sdio.c b/drivers/net/wireless/rsi/rsi_91x_sdio.c index f9c67ed473d1..b35728564c7b 100644 --- a/drivers/net/wireless/rsi/rsi_91x_sdio.c +++ b/drivers/net/wireless/rsi/rsi_91x_sdio.c@@ -929,11 +929,15 @@ static int rsi_sdio_ta_reset(struct rsi_hw *adapter) u32 addr; u8 *data; + data = kzalloc(sizeof(u32), GFP_KERNEL);
Something fishy is going on here. We allocate 4 B but declare data as a u8* (pointer to individual bytes)? In general, dynamically allocating that few bytes is a code smell; either you meant to just use the stack, or this memory's lifetime extends past the lifetime of this stackframe, at which point you probably just meant to stack allocate space in a higher parent frame and pass this preallocated memory down to the child frame to get filled in. Reading through this code, I don't think that the memory is meant to outlive the stack frame. Is there a reason why we can't just declare data as: u8 data [4]; then use ARRAY_SIZE(data) or RSI_9116_REG_SIZE in rsi_reset_chip(), getting rid of the kzalloc/kfree? (Sorry, I hate when a simple fixup becomes a "hey let's rewrite all this code" thus becoming "that guy.") -- Thanks, ~Nick Desaulniers