Re: [PATCH RESEND] drivers: video: metronomefb: avoid out-of-bounds array access
From: Tomi Valkeinen <hidden>
Date: 2014-01-09 12:22:16
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On 2013-11-29 18:51, Michal Nazarewicz wrote:
quoted hunk ↗ jump to hunk
From: Michal Nazarewicz <redacted> load_waveform function checks whether padding bytes in stuff2a and stuff2b are all zero, but does so by treating those arrays as a single longer array. Since the structure is packed, and the size sum matches, it all works, but creates some confusion in the code. This commit changes the stuff2a and stuff2b arrays into pad1 and pad2 fields such that they cover the same bytes as the arrays covered, and changes the check in the load_waveform function so that the fields are read instead of iterating over an arary. It also renames the other “stuff” fields to “ignore*” fields to give them more semantic meaning. Signed-off-by: Michal Nazarewicz <redacted> --- drivers/video/metronomefb.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-)diff --git a/drivers/video/metronomefb.c b/drivers/video/metronomefb.c index 195cc2d..4f36a2b 100644 --- a/drivers/video/metronomefb.c +++ b/drivers/video/metronomefb.c@@ -126,7 +126,7 @@ static struct fb_var_screeninfo metronomefb_var = { /* the waveform structure that is coming from userspace firmware */ struct waveform_hdr { - u8 stuff[32]; + u8 ignore1[32]; u8 wmta[3]; u8 fvsn;@@ -134,13 +134,14 @@ struct waveform_hdr { u8 luts; u8 mc; u8 trc; - u8 stuff3; + u8 ignore2; u8 endb; u8 swtb; - u8 stuff2a[2]; + u32 pad1; /* u16 halfof(pad1) */ - u8 stuff2b[3]; + /* u16 halfof(pad1) */ + u8 pad2;
I don't quite follow what those comments mean... I know nothing of the hw in question, but I guess there's some reason the stuff2a and stuff2b has been separate, and there's even a blank line between. If they pad a particular block in the data structure, doesn't your change make it confusing? It wouldn't be too pad to have those 5 fields as separate ones. One u16 for the stuff2a, and u16 + u8 for the stuff2b. It'd be simple to check that those are zero. Tomi
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