<html><body><p> <pre> On Wed, 2024-10-09 at 08:41 -0700, Guillaume Ranquet wrote: > > External email : Please do not click links or open attachments until > you have verified the sender or the content. > On Fri, 27 Sep 2024 11:03, Liankun Yang <liankun.yang@mediatek.com> > wrote: > >If the len is 0, kernel crash will occur when performing operations. > >Add the len check conditions to prevent kernel crash. > > > >Fixes: f70ac097a2cf ("drm/mediatek: Add MT8195 Embedded DisplayPort > driver") > >Signed-off-by: Liankun Yang <liankun.yang@mediatek.com> > >--- > >Changes in V2: > >- Fix the commit title. > >- Remove blank line between the Fixes and Signe-off-by. > >- Modify the judgment writing method. > >Per suggestion from the previous thread: > > > https://patchwork.kernel.org/project/linux-mediatek/patch/20240925084116.28848-1-liankun.yang@mediatek.com/ > >--- > > drivers/gpu/drm/mediatek/mtk_dp.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > >diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c > b/drivers/gpu/drm/mediatek/mtk_dp.c > >index d8796a904eca..9ecdf62398ee 100644 > >--- a/drivers/gpu/drm/mediatek/mtk_dp.c > >+++ b/drivers/gpu/drm/mediatek/mtk_dp.c > >@@ -1082,7 +1082,7 @@ static void mtk_dp_get_calibration_data(struct > mtk_dp *mtk_dp) > > buf = (u32 *)nvmem_cell_read(cell, &len); > > nvmem_cell_put(cell); > > > >-if (IS_ERR(buf) || ((len / sizeof(u32)) != 4)) { > >+if (IS_ERR(buf) || !len || ((len / sizeof(u32)) != 4)) { > > dev_warn(dev, "Failed to read nvmem_cell_read\n"); > > Hello Liankun, > Would you be able to describe the crash with more details? > > I'm afraid I don't understand the fix? > > if len is 0, dividing 0 by sizeof(u32) is 0 and thus != 4 > So to me, checking for len != 0 is redundant? > > Thx, > Guillaume. Hello Guillaume, Thank you for your correction. The check for len != 0 is redundant. I did not review this patch carefully, and will review it again next time. Thx, Liankun. > > > > if (!IS_ERR(buf)) > >-- > >2.45.2 </pre> </p></body></html><pre>************* MEDIATEK Confidentiality Notice ******************** The information contained in this e-mail message (including any attachments) may be confidential, proprietary, privileged, or otherwise exempt from disclosure under applicable laws. It is intended to be conveyed only to the designated recipient(s). Any use, dissemination, distribution, printing, retaining or copying of this e-mail (including its attachments) by unintended recipient(s) is strictly prohibited and may be unlawful. If you are not an intended recipient of this e-mail, or believe that you have received this e-mail in error, please notify the sender immediately (by replying to this e-mail), delete any and all copies of this e-mail (including any attachments) from your system, and do not disclose the content of this e-mail to any other person. Thank you! </pre>