Re: [PATCH v3] hwmon: (pmbus/q54sj108a2) fix stack overflow in debugfs read

[Guenter Roeck <linux@roeck-us.net>]

On Wed, Mar 04, 2026 at 03:51:17PM -0800, Sanman Pradhan wrote:
> From: Sanman Pradhan <psanman@juniper.net>
> 
> The q54sj108a2_debugfs_read function suffers from a stack buffer overflow
> due to incorrect arguments passed to bin2hex(). The function currently
> passes 'data' as the destination and 'data_char' as the source.
> 
> Because bin2hex() converts each input byte into two hex characters, a
> 32-byte block read results in 64 bytes of output. Since 'data' is only
> 34 bytes (I2C_SMBUS_BLOCK_MAX + 2), this writes 30 bytes past the end
> of the buffer onto the stack.
> 
> Additionally, the arguments were swapped: it was reading from the
> zero-initialized 'data_char' and writing to 'data', resulting in
> all-zero output regardless of the actual I2C read.
> 
> Fix this by:
> 1. Expanding 'data_char' to 66 bytes to safely hold the hex output.
> 2. Correcting the bin2hex() argument order and using the actual read count.
> 3. Using a pointer to select the correct output buffer for the final
>    simple_read_from_buffer call.
> 
> Fixes: d014538aa385 ("hwmon: (pmbus) Driver for Delta power supplies Q54SJ108A2")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sanman Pradhan <psanman@juniper.net>

Applied.

Thanks,
Guenter