From 25dd70a03b1f5f3aa71e1a5091ecd9cd2a13ee43 Mon Sep 17 00:00:00 2001 From: Sanman Pradhan Date: Wed, 4 Mar 2026 15:51:17 -0800 Subject: [PATCH] hwmon: (pmbus/q54sj108a2) fix stack overflow in debugfs read 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 Link: https://lore.kernel.org/r/20260304235116.1045-1-sanman.p211993@gmail.com Signed-off-by: Guenter Roeck --- drivers/hwmon/pmbus/q54sj108a2.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/drivers/hwmon/pmbus/q54sj108a2.c b/drivers/hwmon/pmbus/q54sj108a2.c index fc030ca34480..d5d60a9af8c5 100644 --- a/drivers/hwmon/pmbus/q54sj108a2.c +++ b/drivers/hwmon/pmbus/q54sj108a2.c @@ -79,7 +79,8 @@ static ssize_t q54sj108a2_debugfs_read(struct file *file, char __user *buf, int idx = *idxp; struct q54sj108a2_data *psu = to_psu(idxp, idx); char data[I2C_SMBUS_BLOCK_MAX + 2] = { 0 }; - char data_char[I2C_SMBUS_BLOCK_MAX + 2] = { 0 }; + char data_char[I2C_SMBUS_BLOCK_MAX * 2 + 2] = { 0 }; + char *out = data; char *res; switch (idx) { @@ -150,27 +151,27 @@ static ssize_t q54sj108a2_debugfs_read(struct file *file, char __user *buf, if (rc < 0) return rc; - res = bin2hex(data, data_char, 32); - rc = res - data; - + res = bin2hex(data_char, data, rc); + rc = res - data_char; + out = data_char; break; case Q54SJ108A2_DEBUGFS_FLASH_KEY: rc = i2c_smbus_read_block_data(psu->client, PMBUS_FLASH_KEY_WRITE, data); if (rc < 0) return rc; - res = bin2hex(data, data_char, 4); - rc = res - data; - + res = bin2hex(data_char, data, rc); + rc = res - data_char; + out = data_char; break; default: return -EINVAL; } - data[rc] = '\n'; + out[rc] = '\n'; rc += 2; - return simple_read_from_buffer(buf, count, ppos, data, rc); + return simple_read_from_buffer(buf, count, ppos, out, rc); } static ssize_t q54sj108a2_debugfs_write(struct file *file, const char __user *buf,