From: Len Baker <len.baker@gmx.com> To: Andy Shevchenko <andy.shevchenko@gmail.com> Cc: Len Baker <len.baker@gmx.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Phil Reid <preid@electromag.com.au>, Geert Uytterhoeven <geert@linux-m68k.org>, dri-devel <dri-devel@lists.freedesktop.org>, "open list:FRAMEBUFFER LAYER" <linux-fbdev@vger.kernel.org>, linux-staging@lists.linux.dev, Linux Kernel Mailing List <linux-kernel@vger.kernel.org> Subject: Re: [PATCH v2 1/3] staging/fbtft: Remove all strcpy() uses Date: Sun, 25 Jul 2021 15:58:44 +0200 [thread overview] Message-ID: <20210725135844.GA1953@titan> (raw) In-Reply-To: <CAHp75Vd+ZM_yO6CU_6oJieePMt00Sp6oKEU2+QEyZxLDg5PN8A@mail.gmail.com> Hi, On Sat, Jul 24, 2021 at 11:21:04PM +0300, Andy Shevchenko wrote: > On Sat, Jul 24, 2021 at 7:05 PM Len Baker <len.baker@gmx.com> wrote: > > > > strcpy() performs no bounds checking on the destination buffer. This > > could result in linear overflows beyond the end of the buffer, leading > > to all kinds of misbehaviors. The safe replacement is strscpy() but in > > this case it is simpler to use the "%*ph" format specifier. > > ... > > > - char msg[128]; > > 128 / 4 = 32. So, this buffer is enough to debug print only up to 32 > bytes. Hence %*ph replacement won't cut output earlier than requested. I'm sorry, but I don't understand what you are trying to explain. Moreover, with the "0x%02X " in the sprintf followed by the strcat, the msg buffer can print 128/5 values (25 hex values). The %*ph replacement can print up to 64 bytes, so I don't see any problem here. > > ... > > > + for (j = i + 1; par->init_sequence[j] >= 0; j++); > > Why is i + 1 initial for the j? You may rather access the 'i + 1 + > j'th element in the array... > > ... > > > + par->init_sequence[i], j - i - 1, > > ...and get rid of the ' - i -1' part here. Yes, it was the first idea but I prefer this method since we save aritmethic operations. In other words, if I use what you suggest, the index for par->init_sequence is calculated as a "sum" every iteration. But if the performance is not an issue and you believe that the above is more clear, I have no problem. What do you prefer? Thanks, Len
WARNING: multiple messages have this Message-ID (diff)
From: Len Baker <len.baker@gmx.com> To: Andy Shevchenko <andy.shevchenko@gmail.com> Cc: "open list:FRAMEBUFFER LAYER" <linux-fbdev@vger.kernel.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, linux-staging@lists.linux.dev, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, dri-devel <dri-devel@lists.freedesktop.org>, Len Baker <len.baker@gmx.com>, Geert Uytterhoeven <geert@linux-m68k.org>, Phil Reid <preid@electromag.com.au> Subject: Re: [PATCH v2 1/3] staging/fbtft: Remove all strcpy() uses Date: Sun, 25 Jul 2021 15:58:44 +0200 [thread overview] Message-ID: <20210725135844.GA1953@titan> (raw) In-Reply-To: <CAHp75Vd+ZM_yO6CU_6oJieePMt00Sp6oKEU2+QEyZxLDg5PN8A@mail.gmail.com> Hi, On Sat, Jul 24, 2021 at 11:21:04PM +0300, Andy Shevchenko wrote: > On Sat, Jul 24, 2021 at 7:05 PM Len Baker <len.baker@gmx.com> wrote: > > > > strcpy() performs no bounds checking on the destination buffer. This > > could result in linear overflows beyond the end of the buffer, leading > > to all kinds of misbehaviors. The safe replacement is strscpy() but in > > this case it is simpler to use the "%*ph" format specifier. > > ... > > > - char msg[128]; > > 128 / 4 = 32. So, this buffer is enough to debug print only up to 32 > bytes. Hence %*ph replacement won't cut output earlier than requested. I'm sorry, but I don't understand what you are trying to explain. Moreover, with the "0x%02X " in the sprintf followed by the strcat, the msg buffer can print 128/5 values (25 hex values). The %*ph replacement can print up to 64 bytes, so I don't see any problem here. > > ... > > > + for (j = i + 1; par->init_sequence[j] >= 0; j++); > > Why is i + 1 initial for the j? You may rather access the 'i + 1 + > j'th element in the array... > > ... > > > + par->init_sequence[i], j - i - 1, > > ...and get rid of the ' - i -1' part here. Yes, it was the first idea but I prefer this method since we save aritmethic operations. In other words, if I use what you suggest, the index for par->init_sequence is calculated as a "sum" every iteration. But if the performance is not an issue and you believe that the above is more clear, I have no problem. What do you prefer? Thanks, Len
next prev parent reply other threads:[~2021-07-25 13:59 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-07-24 15:14 [PATCH v2 0/3] Remove all strcpy() uses Len Baker 2021-07-24 15:14 ` Len Baker 2021-07-24 15:14 ` [PATCH v2 1/3] staging/fbtft: " Len Baker 2021-07-24 15:14 ` Len Baker 2021-07-24 20:21 ` Andy Shevchenko 2021-07-24 20:21 ` Andy Shevchenko 2021-07-24 20:21 ` Andy Shevchenko 2021-07-25 13:58 ` Len Baker [this message] 2021-07-25 13:58 ` Len Baker 2021-07-25 18:51 ` Andy Shevchenko 2021-07-25 18:51 ` Andy Shevchenko 2021-07-25 18:51 ` Andy Shevchenko 2021-07-31 13:43 ` Len Baker 2021-07-24 15:14 ` [PATCH v2 2/3] staging/fbtft: Remove unnecessary variable initialization Len Baker 2021-07-24 15:14 ` Len Baker 2021-07-24 15:14 ` [PATCH v2 3/3] staging/fbtft: Fix braces coding style Len Baker 2021-07-24 15:14 ` Len Baker 2021-07-24 18:01 ` Geert Uytterhoeven 2021-07-24 18:01 ` Geert Uytterhoeven 2021-07-24 18:01 ` Geert Uytterhoeven 2021-07-25 14:02 ` Len Baker 2021-07-25 14:02 ` Len Baker
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