* [bug report] out of bounds read parsing vmode commandline option
@ 2017-10-04 12:50 Dan Carpenter
2017-10-04 16:42 ` Geert Uytterhoeven
0 siblings, 1 reply; 3+ messages in thread
From: Dan Carpenter @ 2017-10-04 12:50 UTC (permalink / raw)
To: linux-fbdev
This bug predates git but it looks like it might be simple to fix if the
right person looked at the code.
drivers/video/fbdev/controlfb.c:560 control_setup()
error: buffer overflow 'control_mac_modes' 20 <= 21
drivers/video/fbdev/controlfb.c
549 static void __init control_setup(char *options)
550 {
551 char *this_opt;
552
553 if (!options || !*options)
554 return;
555
556 while ((this_opt = strsep(&options, ",")) != NULL) {
557 if (!strncmp(this_opt, "vmode:", 6)) {
558 int vmode = simple_strtoul(this_opt+6, NULL, 0);
^^^^^
We get vmode from the command line.
559 if (vmode > 0 && vmode <= VMODE_MAX &&
^^^^^^^^^
We check that it's <= 22.
560 control_mac_modes[vmode - 1].m[1] >= 0)
^^^^^^^^^^^^^^^^^
But the problem is that control_mac_modes[] only has 20 elements so the
highest valid index is 19. vmode - 1 can be up to 21.
561 default_vmode = vmode;
562 } else if (!strncmp(this_opt, "cmode:", 6)) {
563 int depth = simple_strtoul(this_opt+6, NULL, 0);
564 switch (depth) {
565 case CMODE_8:
566 case CMODE_16:
567 case CMODE_32:
568 default_cmode = depth;
569 break;
570 case 8:
571 default_cmode = CMODE_8;
572 break;
573 case 15:
574 case 16:
575 default_cmode = CMODE_16;
576 break;
577 case 24:
578 case 32:
579 default_cmode = CMODE_32;
580 break;
581 }
582 }
583 }
584 }
regards,
dan carpenter
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [bug report] out of bounds read parsing vmode commandline option 2017-10-04 12:50 [bug report] out of bounds read parsing vmode commandline option Dan Carpenter @ 2017-10-04 16:42 ` Geert Uytterhoeven [not found] ` <CGME20171017133722epcas2p1361446d57dfad4ef9a9bc2a0a247e70a@epcas2p1.samsung.com> 0 siblings, 1 reply; 3+ messages in thread From: Geert Uytterhoeven @ 2017-10-04 16:42 UTC (permalink / raw) To: Dan Carpenter Cc: Linux Fbdev development list, linuxppc-dev@lists.ozlabs.org, Benjamin Herrenschmidt Hi Dan, On Wed, Oct 4, 2017 at 2:50 PM, Dan Carpenter <dan.carpenter@oracle.com> wrote: > This bug predates git but it looks like it might be simple to fix if the > right person looked at the code. > > drivers/video/fbdev/controlfb.c:560 control_setup() > error: buffer overflow 'control_mac_modes' 20 <= 21 > > drivers/video/fbdev/controlfb.c > 549 static void __init control_setup(char *options) > 550 { > 551 char *this_opt; > 552 > 553 if (!options || !*options) > 554 return; > 555 > 556 while ((this_opt = strsep(&options, ",")) != NULL) { > 557 if (!strncmp(this_opt, "vmode:", 6)) { > 558 int vmode = simple_strtoul(this_opt+6, NULL, 0); > ^^^^^ > We get vmode from the command line. > > 559 if (vmode > 0 && vmode <= VMODE_MAX && > ^^^^^^^^^ > We check that it's <= 22. > > 560 control_mac_modes[vmode - 1].m[1] >= 0) > ^^^^^^^^^^^^^^^^^ > But the problem is that control_mac_modes[] only has 20 elements so the > highest valid index is 19. vmode - 1 can be up to 21. Nice catch! The bug was introduced in v2.4.5.6, when 2 new modes were added to macmodes.h, but control_mac_modes[] wasn't updated: https://kernel.opensuse.org/cgit/kernel/diff/include/video/macmodes.h?h=v2.5.2&id)f279c764808560eaceb88fef36cbc35c529aad A simple fix is to check against ARRAY_SIZE(control_mac_modes) instead. A better fix is to add the missing entries to control_mac_modes[], cfr. the (gmail-whitespace-damaged) patch below: --- a/drivers/video/fbdev/controlfb.h +++ b/drivers/video/fbdev/controlfb.h @@ -141,5 +141,7 @@ static struct max_cmodes control_mac_modes[] = { {{ 1, 2}}, /* 1152x870, 75Hz */ {{ 0, 1}}, /* 1280x960, 75Hz */ {{ 0, 1}}, /* 1280x1024, 75Hz */ + {{ 1, 2}}, /* 1152x768, 60Hz */ + {{ 0, 1}}, /* 1600x1024, 60Hz */ }; (this array lists the maximum color mode (8, 16, or 32 bpp) for each video mode given RAM restrictions (2 or 4 MiB)). The 1152x768 mode is probably OK. Given the 1600x1024 mode has a lower dotclock (112 MHz) than the supported 1280x960 mode, it's probably OK, too. platinum_reg_init[] and valkyrie_reg_init[] seem to be handled fine. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds ^ permalink raw reply [flat|nested] 3+ messages in thread
[parent not found: <CGME20171017133722epcas2p1361446d57dfad4ef9a9bc2a0a247e70a@epcas2p1.samsung.com>]
* Re: [bug report] out of bounds read parsing vmode commandline option [not found] ` <CGME20171017133722epcas2p1361446d57dfad4ef9a9bc2a0a247e70a@epcas2p1.samsung.com> @ 2017-10-17 13:37 ` Bartlomiej Zolnierkiewicz 0 siblings, 0 replies; 3+ messages in thread From: Bartlomiej Zolnierkiewicz @ 2017-10-17 13:37 UTC (permalink / raw) To: Geert Uytterhoeven Cc: Dan Carpenter, Linux Fbdev development list, linuxppc-dev@lists.ozlabs.org, Benjamin Herrenschmidt Hi, On Wednesday, October 04, 2017 06:42:37 PM Geert Uytterhoeven wrote: > Hi Dan, > > On Wed, Oct 4, 2017 at 2:50 PM, Dan Carpenter <dan.carpenter@oracle.com> wrote: > > This bug predates git but it looks like it might be simple to fix if the > > right person looked at the code. > > > > drivers/video/fbdev/controlfb.c:560 control_setup() > > error: buffer overflow 'control_mac_modes' 20 <= 21 > > > > drivers/video/fbdev/controlfb.c > > 549 static void __init control_setup(char *options) > > 550 { > > 551 char *this_opt; > > 552 > > 553 if (!options || !*options) > > 554 return; > > 555 > > 556 while ((this_opt = strsep(&options, ",")) != NULL) { > > 557 if (!strncmp(this_opt, "vmode:", 6)) { > > 558 int vmode = simple_strtoul(this_opt+6, NULL, 0); > > ^^^^^ > > We get vmode from the command line. > > > > 559 if (vmode > 0 && vmode <= VMODE_MAX && > > ^^^^^^^^^ > > We check that it's <= 22. > > > > 560 control_mac_modes[vmode - 1].m[1] >= 0) > > ^^^^^^^^^^^^^^^^^ > > But the problem is that control_mac_modes[] only has 20 elements so the > > highest valid index is 19. vmode - 1 can be up to 21. > > Nice catch! > > The bug was introduced in v2.4.5.6, when 2 new modes were added to > macmodes.h, but control_mac_modes[] wasn't updated: > > https://kernel.opensuse.org/cgit/kernel/diff/include/video/macmodes.h?h=v2.5.2&id)f279c764808560eaceb88fef36cbc35c529aad > > A simple fix is to check against ARRAY_SIZE(control_mac_modes) instead. > > A better fix is to add the missing entries to control_mac_modes[], cfr. the > (gmail-whitespace-damaged) patch below: > > --- a/drivers/video/fbdev/controlfb.h > +++ b/drivers/video/fbdev/controlfb.h > @@ -141,5 +141,7 @@ static struct max_cmodes control_mac_modes[] = { > {{ 1, 2}}, /* 1152x870, 75Hz */ > {{ 0, 1}}, /* 1280x960, 75Hz */ > {{ 0, 1}}, /* 1280x1024, 75Hz */ > + {{ 1, 2}}, /* 1152x768, 60Hz */ > + {{ 0, 1}}, /* 1600x1024, 60Hz */ > }; > > (this array lists the maximum color mode (8, 16, or 32 bpp) for each > video mode given RAM restrictions (2 or 4 MiB)). > > The 1152x768 mode is probably OK. Given the 1600x1024 mode has a lower > dotclock (112 MHz) than the supported 1280x960 mode, it's probably OK, too. Looks fine to me, could you please submit it as a normal patch? Best regards, -- Bartlomiej Zolnierkiewicz Samsung R&D Institute Poland Samsung Electronics ^ permalink raw reply [flat|nested] 3+ messages in thread
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2017-10-04 12:50 [bug report] out of bounds read parsing vmode commandline option Dan Carpenter
2017-10-04 16:42 ` Geert Uytterhoeven
[not found] ` <CGME20171017133722epcas2p1361446d57dfad4ef9a9bc2a0a247e70a@epcas2p1.samsung.com>
2017-10-17 13:37 ` Bartlomiej Zolnierkiewicz
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