On Mon, Sep 27, 2021 at 02:41:40PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> Building the bpmp-debugfs driver for Arm results in a warning for stack usage:
>
> drivers/firmware/tegra/bpmp-debugfs.c:321:16: error: stack frame size of 1224 bytes in function 'bpmp_debug_store' [-Werror,-Wframe-larger-than=]
> static ssize_t bpmp_debug_store(struct file *file, const char __user *buf,
>
> It should be possible to rearrange the code to not require two separate
> buffers for the file name, but the easiest workaround is to use dynamic
> allocation.
>
> Fixes: 5e37b9c137ee ("firmware: tegra: Add support for in-band debug")
> Link: https://lore.kernel.org/all/20201204193714.3134651-1-arnd@xxxxxxxxxx/
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
> I sent this one in 2020 but got no reply. It still appears to be
> required, please have a look.
> ---
> drivers/firmware/tegra/bpmp-debugfs.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
If this is not a problem on 64-bit ARM, then perhaps we should add that
as a dependency. BPMP is only available in Tegra210 and later, all of
which are 64-bit.
But dynamic allocation also doesn't sound that bad. This is debugfs
support, after all, so shouldn't be in any fast path.
>
> diff --git a/drivers/firmware/tegra/bpmp-debugfs.c b/drivers/firmware/tegra/bpmp-debugfs.c
> index 3e9fa4b54358..f6888cee83ee 100644
> --- a/drivers/firmware/tegra/bpmp-debugfs.c
> +++ b/drivers/firmware/tegra/bpmp-debugfs.c
> @@ -74,28 +74,34 @@ static void seqbuf_seek(struct seqbuf *seqbuf, ssize_t offset)
> static const char *get_filename(struct tegra_bpmp *bpmp,
> const struct file *file, char *buf, int size)
> {
> - char root_path_buf[512];
> + char *root_path_buf;
> const char *root_path;
> - const char *filename;
> + const char *filename = NULL;
> size_t root_len;
>
> + root_path_buf = kzalloc(512, GFP_KERNEL);
> + if (!root_path_buf)
> + goto out;
> +
> root_path = dentry_path(bpmp->debugfs_mirror, root_path_buf,
> sizeof(root_path_buf));
> if (IS_ERR(root_path))
> - return NULL;
> + goto out;
>
> root_len = strlen(root_path);
>
> filename = dentry_path(file->f_path.dentry, buf, size);
> if (IS_ERR(filename))
> - return NULL;
> + goto out;
Shouldn't this and...
> if (strlen(filename) < root_len ||
> strncmp(filename, root_path, root_len))
> - return NULL;
> + goto out;
this reset filename to NULL? All callers check for !filename as their
error condition.
I can fix that up as I apply this, but perhaps shout if you did this on
purpose and it needs to stay this way.
Thierry
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