On 23/03/2021 14.04, Arnd Bergmann wrote:
From: Arnd Bergmann arnd@arndb.de
gcc warns about an sprintf() that uses the same buffer as source and destination, which is undefined behavior in C99:
drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c: In function 'amdgpu_securedisplay_debugfs_write': drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c:141:6: error: 'sprintf' argument 3 overlaps destination object 'i2c_output' [-Werror=restrict] 141 | sprintf(i2c_output, "%s 0x%X", i2c_output, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 142 | securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf[i]); | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c:97:7: note: destination object referenced by 'restrict'-qualified argument 1 was declared here 97 | char i2c_output[256]; | ^~~~~~~~~~
Rewrite it to remember the current offset into the buffer instead.
Signed-off-by: Arnd Bergmann arnd@arndb.de
drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c index 834440ab9ff7..69d7f6bff5d4 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c @@ -136,9 +136,10 @@ static ssize_t amdgpu_securedisplay_debugfs_write(struct file *f, const char __u ret = psp_securedisplay_invoke(psp, TA_SECUREDISPLAY_COMMAND__SEND_ROI_CRC); if (!ret) { if (securedisplay_cmd->status == TA_SECUREDISPLAY_STATUS__SUCCESS) {
int pos = 0; memset(i2c_output, 0, sizeof(i2c_output)); for (i = 0; i < TA_SECUREDISPLAY_I2C_BUFFER_SIZE; i++)
sprintf(i2c_output, "%s 0x%X", i2c_output,
pos += sprintf(i2c_output + pos, " 0x%X", securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf[i]); dev_info(adev->dev, "SECUREDISPLAY: I2C buffer out put is :%s\n", i2c_output);
Eh, why not get rid of the 256 byte stack allocation and just replace all of this by
dev_info(adev->dev, ""SECUREDISPLAY: I2C buffer out put is: %*ph\n", TA_SECUREDISPLAY_I2C_BUFFER_SIZE, securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf);
That's much less code (both in #LOC and .text), and avoids adding yet another place that will be audited over and over for "hm, yeah, that sprintf() is actually not gonna overflow".
Yeah, it'll lose the 0x prefixes for each byte and use lowercase hex chars.
Rasmus