On 7/14/2022 9:13 PM, André Almeida
wrote:
Às 12:06 de 14/07/22, Sebin Sebastian escreveu:On Tue, Jul 12, 2022 at 12:14:27PM -0300, André Almeida wrote:Hi Sebin, Às 10:29 de 10/07/22, Sebin Sebastian escreveu:Fix two coverity warning's double free and and an uninitialized pointer read. Both tmp and new are pointing at same address and both are freed which leads to double free. Freeing tmp in the condition after new is assigned with new address fixes the double free issue. new is not initialized to null which also leads to a free on an uninitialized pointer. Coverity issue: 1518665 (uninitialized pointer read) 1518679 (double free)What are those numbers?These numbers are the issue ID's for the errors that are being reported by the coverity static analyzer tool.I see, but I don't know which tool was used, so those seem like random number to me. I would just remove this part of your commit message, but if you want to keep it, you need to at least mention what's the tool.
new variable is not needed to initialize.
The only condition double free happens is:
tmp = new;
if (sscanf(reg_offset, "%X %n", &tmp[i],
&ret) != 1) {
ret = -EINVAL;
goto error_free; // if it hits
this
}
and can be avoided like:
- kfree(tmp);
+ if (tmp != new)
+ kfree(tmp);
kfree(new);
return ret;
}
Regards,
S.Amarnath
Signed-off-by: Sebin Sebastian <mailmesebin00@xxxxxxxxx> --- drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c index f3b3c688e4e7..d82fe0e1b06b 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c @@ -1660,7 +1660,7 @@ static ssize_t amdgpu_reset_dump_register_list_write(struct file *f, { struct amdgpu_device *adev = (struct amdgpu_device *)file_inode(f)->i_private; char reg_offset[11]; - uint32_t *new, *tmp = NULL; + uint32_t *new = NULL, *tmp = NULL; int ret, i = 0, len = 0; do { @@ -1692,17 +1692,19 @@ static ssize_t amdgpu_reset_dump_register_list_write(struct file *f, goto error_free; }If the `if (!new) {` above this line is true, will be tmp freed?Yes, It doesn't seem to free tmp here. Should I free tmp immediately after the do while loop and remove `kfree(tmp)` from the `if (ret)` block? Thanks for pointing out the errors.If you free immediately after the while loop, then you would risk a use after free here: swap(adev->reset_dump_reg_list, tmp); So this isn't the solution either.ret = down_write_killable(&adev->reset_domain->sem); - if (ret) + if (ret) { + kfree(tmp); goto error_free; + } swap(adev->reset_dump_reg_list, tmp); swap(adev->reset_dump_reg_value, new); adev->num_regs = i; up_write(&adev->reset_domain->sem); + kfree(tmp); ret = size; error_free: - kfree(tmp); kfree(new); return ret; }
