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. So, this serie removes all strcpy uses from the "staging/fbtft" subsystem.
Also, refactor the code a bit to follow the kernel coding-style and avoid unnecessary variable initialization.
Changelog v1 -> v2 - Add two new commits to clean the code. - Use the "%*ph" format specifier instead of strscpy() function (Geert Uytterhoeven)
Len Baker (3): staging/fbtft: Remove all strcpy() uses staging/fbtft: Remove unnecessary variable initialization staging/fbtft: Fix braces coding style
drivers/staging/fbtft/fbtft-core.c | 30 +++++++++++++----------------- 1 file changed, 13 insertions(+), 17 deletions(-)
-- 2.25.1
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.
Signed-off-by: Len Baker len.baker@gmx.com --- drivers/staging/fbtft/fbtft-core.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-)
diff --git a/drivers/staging/fbtft/fbtft-core.c b/drivers/staging/fbtft/fbtft-core.c index 3723269890d5..be20da3c4a5c 100644 --- a/drivers/staging/fbtft/fbtft-core.c +++ b/drivers/staging/fbtft/fbtft-core.c @@ -992,8 +992,6 @@ static int fbtft_init_display_from_property(struct fbtft_par *par) int fbtft_init_display(struct fbtft_par *par) { int buf[64]; - char msg[128]; - char str[16]; int i = 0; int j;
@@ -1036,17 +1034,14 @@ int fbtft_init_display(struct fbtft_par *par) switch (par->init_sequence[i]) { case -1: i++; + /* make debug message */ - strcpy(msg, ""); - j = i + 1; - while (par->init_sequence[j] >= 0) { - sprintf(str, "0x%02X ", par->init_sequence[j]); - strcat(msg, str); - j++; - } + for (j = i + 1; par->init_sequence[j] >= 0; j++); + fbtft_par_dbg(DEBUG_INIT_DISPLAY, par, - "init: write(0x%02X) %s\n", - par->init_sequence[i], msg); + "init: write(0x%02X) %*ph\n", + par->init_sequence[i], j - i - 1, + &par->init_sequence[i + 1]);
/* Write */ j = 0; -- 2.25.1
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.
...
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.
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
On Sun, Jul 25, 2021 at 4:59 PM Len Baker len.baker@gmx.com wrote:
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:
...
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.
Right. That's what I am trying to say and the hint here is to combine this part into a phrase in the commit message in the next version of the patch.
...
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?
I prefer my variant and I believe the compilers nowadays are clever enough to understand this. Have you tried to compile and compare the real assembly?
On Sun, Jul 25, 2021 at 09:51:18PM +0300, Andy Shevchenko wrote:
On Sun, Jul 25, 2021 at 4:59 PM Len Baker len.baker@gmx.com wrote:
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:
...
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.
Right. That's what I am trying to say and the hint here is to combine this part into a phrase in the commit message in the next version of the patch.
Ok, I will update the commit changelog for the next version.
...
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?
I prefer my variant and I believe the compilers nowadays are clever enough to understand this.
Ok, understood. Thanks.
Have you tried to compile and compare the real assembly?
I will test it.
-- With Best Regards, Andy Shevchenko
Regards, Len
Remove the initialization of the variable "i" since it is written a few lines later.
Signed-off-by: Len Baker len.baker@gmx.com --- drivers/staging/fbtft/fbtft-core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/fbtft/fbtft-core.c b/drivers/staging/fbtft/fbtft-core.c index be20da3c4a5c..cc2bee22f7ad 100644 --- a/drivers/staging/fbtft/fbtft-core.c +++ b/drivers/staging/fbtft/fbtft-core.c @@ -992,7 +992,7 @@ static int fbtft_init_display_from_property(struct fbtft_par *par) int fbtft_init_display(struct fbtft_par *par) { int buf[64]; - int i = 0; + int i; int j;
/* sanity check */ -- 2.25.1
Add braces to the "for" loop and remove braces from the "if" statement. This way the kernel coding style is followed.
Signed-off-by: Len Baker len.baker@gmx.com --- drivers/staging/fbtft/fbtft-core.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/drivers/staging/fbtft/fbtft-core.c b/drivers/staging/fbtft/fbtft-core.c index cc2bee22f7ad..d87792649efe 100644 --- a/drivers/staging/fbtft/fbtft-core.c +++ b/drivers/staging/fbtft/fbtft-core.c @@ -1003,9 +1003,11 @@ int fbtft_init_display(struct fbtft_par *par) }
/* make sure stop marker exists */ - for (i = 0; i < FBTFT_MAX_INIT_SEQUENCE; i++) + for (i = 0; i < FBTFT_MAX_INIT_SEQUENCE; i++) { if (par->init_sequence[i] == -3) break; + } + if (i == FBTFT_MAX_INIT_SEQUENCE) { dev_err(par->info->device, "missing stop marker at end of init sequence\n"); @@ -1016,10 +1018,9 @@ int fbtft_init_display(struct fbtft_par *par)
i = 0; while (i < FBTFT_MAX_INIT_SEQUENCE) { - if (par->init_sequence[i] == -3) { - /* done */ - return 0; - } + if (par->init_sequence[i] == -3) + return 0; /* done */ + if (par->init_sequence[i] >= 0) { dev_err(par->info->device, "missing delimiter at position %d\n", i); -- 2.25.1
Hi Len,
On Sat, Jul 24, 2021 at 7:44 PM Len Baker len.baker@gmx.com wrote:
Add braces to the "for" loop and remove braces from the "if" statement. This way the kernel coding style is followed.
Signed-off-by: Len Baker len.baker@gmx.com
Thanks for your patch!
--- a/drivers/staging/fbtft/fbtft-core.c +++ b/drivers/staging/fbtft/fbtft-core.c
@@ -1016,10 +1018,9 @@ int fbtft_init_display(struct fbtft_par *par)
i = 0; while (i < FBTFT_MAX_INIT_SEQUENCE) {
if (par->init_sequence[i] == -3) {/* done */return 0;}
These braces should not be removed, due to the presence of the comment.
if (par->init_sequence[i] == -3)return 0; /* done */if (par->init_sequence[i] >= 0) { dev_err(par->info->device, "missing delimiter at position %d\n", i);
Gr{oetje,eeting}s,
Geert
Hi,
On Sat, Jul 24, 2021 at 08:01:53PM +0200, Geert Uytterhoeven wrote:
Hi Len,
On Sat, Jul 24, 2021 at 7:44 PM Len Baker len.baker@gmx.com wrote:
Add braces to the "for" loop and remove braces from the "if" statement. This way the kernel coding style is followed.
Signed-off-by: Len Baker len.baker@gmx.com
Thanks for your patch!
--- a/drivers/staging/fbtft/fbtft-core.c +++ b/drivers/staging/fbtft/fbtft-core.c
@@ -1016,10 +1018,9 @@ int fbtft_init_display(struct fbtft_par *par)
i = 0; while (i < FBTFT_MAX_INIT_SEQUENCE) {
if (par->init_sequence[i] == -3) {/* done */return 0;}These braces should not be removed, due to the presence of the comment.
Ok, I leave it as is.
Thanks, Len
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