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Mon, 20 Oct 2025 10:49:02 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id mjY2Ap4T9mhCUgAAD6G6ig (envelope-from ); Mon, 20 Oct 2025 10:49:02 +0000 Message-ID: <3aa0ef90-22e1-4531-b059-57d924c44011@suse.de> Date: Mon, 20 Oct 2025 12:49:01 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drm/tiny: Use kmalloc_array() instead of kmalloc() To: Jani Nikula , Mehdi Ben Hadj Khelifa , Greg KH Cc: lanzano.alex@gmail.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, airlied@gmail.com, simona@ffwll.ch, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, david.hunter.linux@gmail.com, khalid@kernel.org, linux-kernel-mentees@lists.linuxfoundation.org References: <20251019151247.171558-1-mehdi.benhadjkhelifa@gmail.com> <2025101910-dipper-suburb-1755@gregkh> <02e617bec795d2ef371069f2d5fb954dfb31a450@intel.com> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; keydata= xsBNBFs50uABCADEHPidWt974CaxBVbrIBwqcq/WURinJ3+2WlIrKWspiP83vfZKaXhFYsdg XH47fDVbPPj+d6tQrw5lPQCyqjwrCPYnq3WlIBnGPJ4/jreTL6V+qfKRDlGLWFjZcsrPJGE0 BeB5BbqP5erN1qylK9i3gPoQjXGhpBpQYwRrEyQyjuvk+Ev0K1Jc5tVDeJAuau3TGNgah4Yc hdHm3bkPjz9EErV85RwvImQ1dptvx6s7xzwXTgGAsaYZsL8WCwDaTuqFa1d1jjlaxg6+tZsB 9GluwvIhSezPgnEmimZDkGnZRRSFiGP8yjqTjjWuf0bSj5rUnTGiyLyRZRNGcXmu6hjlABEB AAHNJ1Rob21hcyBaaW1tZXJtYW5uIDx0emltbWVybWFubkBzdXNlLmRlPsLAjgQTAQgAOAIb AwULCQgHAgYVCgkICwIEFgIDAQIeAQIXgBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftODH AAoJEGgNwR1TC3ojx1wH/0hKGWugiqDgLNXLRD/4TfHBEKmxIrmfu9Z5t7vwUKfwhFL6hqvo lXPJJKQpQ2z8+X2vZm/slsLn7J1yjrOsoJhKABDi+3QWWSGkaGwRJAdPVVyJMfJRNNNIKwVb U6B1BkX2XDKDGffF4TxlOpSQzdtNI/9gleOoUA8+jy8knnDYzjBNOZqLG2FuTdicBXblz0Mf vg41gd9kCwYXDnD91rJU8tzylXv03E75NCaTxTM+FBXPmsAVYQ4GYhhgFt8S2UWMoaaABLDe 7l5FdnLdDEcbmd8uLU2CaG4W2cLrUaI4jz2XbkcPQkqTQ3EB67hYkjiEE6Zy3ggOitiQGcqp j//OwE0EWznS4AEIAMYmP4M/V+T5RY5at/g7rUdNsLhWv1APYrh9RQefODYHrNRHUE9eosYb T6XMryR9hT8XlGOYRwKWwiQBoWSDiTMo/Xi29jUnn4BXfI2px2DTXwc22LKtLAgTRjP+qbU6 3Y0xnQN29UGDbYgyyK51DW3H0If2a3JNsheAAK+Xc9baj0LGIc8T9uiEWHBnCH+RdhgATnWW GKdDegUR5BkDfDg5O/FISymJBHx2Dyoklv5g4BzkgqTqwmaYzsl8UxZKvbaxq0zbehDda8lv hFXodNFMAgTLJlLuDYOGLK2AwbrS3Sp0AEbkpdJBb44qVlGm5bApZouHeJ/+n+7r12+lqdsA EQEAAcLAdgQYAQgAIAIbDBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftOH6AAoJEGgNwR1T C3ojVSkIALpAPkIJPQoURPb1VWjh34l0HlglmYHvZszJWTXYwavHR8+k6Baa6H7ufXNQtThR yIxJrQLW6rV5lm7TjhffEhxVCn37+cg0zZ3j7zIsSS0rx/aMwi6VhFJA5hfn3T0TtrijKP4A SAQO9xD1Zk9/61JWk8OysuIh7MXkl0fxbRKWE93XeQBhIJHQfnc+YBLprdnxR446Sh8Wn/2D Ya8cavuWf2zrB6cZurs048xe0UbSW5AOSo4V9M0jzYI4nZqTmPxYyXbm30Kvmz0rYVRaitYJ 4kyYYMhuULvrJDMjZRvaNe52tkKAvMevcGdt38H4KSVXAylqyQOW5zvPc4/sq9c= In-Reply-To: <02e617bec795d2ef371069f2d5fb954dfb31a450@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Level: X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; TAGGED_RCPT(0.00)[]; RCVD_TLS_ALL(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_TWELVE(0.00)[14]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; FREEMAIL_TO(0.00)[linux.intel.com,gmail.com,linuxfoundation.org]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; TO_DN_SOME(0.00)[]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[gmail.com,linux.intel.com,kernel.org,ffwll.ch,lists.freedesktop.org,vger.kernel.org,linuxfoundation.org,lists.linuxfoundation.org]; MID_RHS_MATCH_FROM(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,imap1.dmz-prg2.suse.org:helo] X-Spam-Flag: NO X-Spam-Score: -2.80 Hi Am 20.10.25 um 11:50 schrieb Jani Nikula: > On Sun, 19 Oct 2025, Mehdi Ben Hadj Khelifa wrote: >> On 10/19/25 3:47 PM, Thomas Zimmermann wrote: >>> Hi >>> >>> Am 19.10.25 um 16:34 schrieb Greg KH: >>>> On Sun, Oct 19, 2025 at 04:12:28PM +0100, Mehdi Ben Hadj Khelifa wrote: >>>>> Replace kmalloc() with kmalloc_array() to correctly >>>>> handle array allocations and benefit from built-in overflow checking[1]. >>>>> >>>>> [1]:https://docs.kernel.org/process/deprecated.html >>>>> >>>>> Signed-off-by: Mehdi Ben Hadj Khelifa >>>>> --- >>>>>   drivers/gpu/drm/tiny/repaper.c | 2 +- >>>>>   1 file changed, 1 insertion(+), 1 deletion(-) >>>>> >>>>> diff --git a/drivers/gpu/drm/tiny/repaper.c b/drivers/gpu/drm/tiny/ >>>>> repaper.c >>>>> index 4824f863fdba..290132c24ff9 100644 >>>>> --- a/drivers/gpu/drm/tiny/repaper.c >>>>> +++ b/drivers/gpu/drm/tiny/repaper.c >>>>> @@ -534,7 +534,7 @@ static int repaper_fb_dirty(struct >>>>> drm_framebuffer *fb, const struct iosys_map * >>>>>       DRM_DEBUG("Flushing [FB:%d] st=%ums\n", fb->base.id, >>>>>             epd->factored_stage_time); >>>>> -    buf = kmalloc(fb->width * fb->height / 8, GFP_KERNEL); >>>>> +    buf = kmalloc_array(fb->height / 8, fb->width, GFP_KERNEL); > Also worth emphasizing that this is wildly wrong for any height that is > not a multiple of 8. Yes. I skipped over details as the format helpers would solve this problem if done correctly. > > And I thought I shot down a similar patch not long ago. You did AFAIR. > > Is there some tool that suggests doing this? Fix the tool instead > please. There's this todo item that the patch refers to. Volunteers discover these and start working. But without mentoring, it's often not to anyone's benefit. I've noticed a similar pattern wrt the DRM todo list. Best regards Thomas > > BR, > Jani. > > > > >>>> This isn't an array, so this function change doesn't seem to make much >>>> sense, right?  The size should have already been checked earlier in the >>>> call change to be correct. >> Yes,I was intending to say framebuffer but I was working on another >> similar patch simultaneously so I reused same words by mistake. Thanks >> for clarifying that.> >>> Yes, we've recently received plenty of these pointless changes. The >>> correct code would compute the number of bytes per pixel using >>> drm_format_info_min_pitch() and multiply with fb->height. The latter >>> could (maybe) use kmalloc_array(). It would still not be an array in the >>> common sense. >>> >> Thanks for the review and suggestion.I will be sending a v2 patch with >> the recommended code change. >> >> Best Regards, >> Mehdi Ben Hadj Khelifa> Best regards >>> Thomas >>> >>>> thanks, >>>> >>>> greg k-h >>> -- >>> -- >>> Thomas Zimmermann >>> Graphics Driver Developer >>> SUSE Software Solutions Germany GmbH >>> Frankenstrasse 146, 90461 Nuernberg, Germany >>> GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman >>> HRB 36809 (AG Nuernberg) -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)