From 70f758da9596e63f983193d3324a37af3a522ebf Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Sun, 26 Feb 2006 19:19:08 -0300 Subject: bttv: correct bttv_risc_packed buffer size From: Duncan Sands This patch fixes the strange crashes I was seeing after using bttv card, caused by a buffer overflow in bttv_risc_packed. The instruction buffer size calculation contains two errors: (a) a non-zero padding value can push the start of the next bpl section to just before a page border, leading to more scanline splits and thus additional instructions. (b) the first DMA region can be smaller than one page, so there can be a scanline split even if bpl*lines is smaller than PAGE_SIZE. For example, consider the case where offset is 0, bpl is 2, padding is 4094, lines is smaller than 2048, the first DMA region has size 1 and all others have size PAGE_SIZE, assumed to equal 4096. Then all bpl regions cross page borders and the number of instructions written is 2*lines+2, rather than lines+2 (the current estimate). With this patch the number of instructions for this example is estimated to be 2*lines+3. Also, the BUG_ON that was supposed to catch buffer overflows contained a thinko causing it fire only if the buffer was overrun by a factor of 16 or more, so it fixes the the BUG_ON's (using sizeof rather than "4"). Signed-off-by: Duncan Sands Signed-off-by: Mauro Carvalho Chehab --- linux/drivers/media/video/bttv-risc.c | 12 +++++++----- linux/drivers/media/video/cx88/cx88-core.c | 4 ++-- 2 files changed, 9 insertions(+), 7 deletions(-) (limited to 'linux/drivers') diff --git a/linux/drivers/media/video/bttv-risc.c b/linux/drivers/media/video/bttv-risc.c index acceee39a..4efe74dd8 100644 --- a/linux/drivers/media/video/bttv-risc.c +++ b/linux/drivers/media/video/bttv-risc.c @@ -52,8 +52,10 @@ bttv_risc_packed(struct bttv *btv, struct btcx_riscmem *risc, int rc; /* estimate risc mem: worst case is one write per page border + - one write per scan line + sync + jump (all 2 dwords) */ - instructions = (bpl * lines) / PAGE_SIZE + lines; + one write per scan line + sync + jump (all 2 dwords). padding + can cause next bpl to start close to a page border. First DMA + region may be smaller than PAGE_SIZE */ + instructions = 1 + ((bpl + padding) * lines) / PAGE_SIZE + lines; instructions += 2; if ((rc = btcx_riscmem_alloc(btv->c.pci,risc,instructions*8)) < 0) return rc; @@ -105,7 +107,7 @@ bttv_risc_packed(struct bttv *btv, struct btcx_riscmem *risc, /* save pointer to jmp instruction address */ risc->jmp = rp; - BUG_ON((risc->jmp - risc->cpu + 2) / 4 > risc->size); + BUG_ON((risc->jmp - risc->cpu + 2) * sizeof(*risc->cpu) > risc->size); return 0; } @@ -223,7 +225,7 @@ bttv_risc_planar(struct bttv *btv, struct btcx_riscmem *risc, /* save pointer to jmp instruction address */ risc->jmp = rp; - BUG_ON((risc->jmp - risc->cpu + 2) / 4 > risc->size); + BUG_ON((risc->jmp - risc->cpu + 2) * sizeof(*risc->cpu) > risc->size); return 0; } @@ -308,7 +310,7 @@ bttv_risc_overlay(struct bttv *btv, struct btcx_riscmem *risc, /* save pointer to jmp instruction address */ risc->jmp = rp; - BUG_ON((risc->jmp - risc->cpu + 2) / 4 > risc->size); + BUG_ON((risc->jmp - risc->cpu + 2) * sizeof(*risc->cpu) > risc->size); kfree(skips); return 0; } diff --git a/linux/drivers/media/video/cx88/cx88-core.c b/linux/drivers/media/video/cx88/cx88-core.c index d3f993b6a..24acfa2bd 100644 --- a/linux/drivers/media/video/cx88/cx88-core.c +++ b/linux/drivers/media/video/cx88/cx88-core.c @@ -180,7 +180,7 @@ int cx88_risc_buffer(struct pci_dev *pci, struct btcx_riscmem *risc, /* save pointer to jmp instruction address */ risc->jmp = rp; - BUG_ON((risc->jmp - risc->cpu + 2) / 4 > risc->size); + BUG_ON((risc->jmp - risc->cpu + 2) * sizeof (*risc->cpu) > risc->size); return 0; } @@ -205,7 +205,7 @@ int cx88_risc_databuffer(struct pci_dev *pci, struct btcx_riscmem *risc, /* save pointer to jmp instruction address */ risc->jmp = rp; - BUG_ON((risc->jmp - risc->cpu + 2) / 4 > risc->size); + BUG_ON((risc->jmp - risc->cpu + 2) * sizeof (*risc->cpu) > risc->size); return 0; } -- cgit v1.2.3