Danilo Krummrich
2024-Apr-05 15:53 UTC
[PATCH] drm: nv04: Add check to avoid out of bounds access
On 3/31/24 08:45, Mikhail Kobuk wrote:> Output Resource (dcb->or) value is not guaranteed to be non-zero (i.e. > in drivers/gpu/drm/nouveau/nouveau_bios.c, in 'fabricate_dcb_encoder_table()' > 'dcb->or' is assigned value '0' in call to 'fabricate_dcb_output()').I don't really know much about the semantics of this code. Looking at fabricate_dcb_output() though I wonder if the intention was to assign BIT(or) to entry->or. @Lyude, can you help here? Otherwise, for parsing the DCB entries, it seems that the bound checks are happening in olddcb_outp_foreach() [1]. [1] https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/nouveau/nouveau_bios.c#L1331> > Add check to validate 'dcb->or' before it's used. > > Found by Linux Verification Center (linuxtesting.org) with SVACE. > > Fixes: 2e5702aff395 ("drm/nouveau: fabricate DCB encoder table for iMac G4") > Signed-off-by: Mikhail Kobuk <m.kobuk at ispras.ru> > --- > drivers/gpu/drm/nouveau/dispnv04/dac.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/nouveau/dispnv04/dac.c b/drivers/gpu/drm/nouveau/dispnv04/dac.c > index d6b8e0cce2ac..0c8d4fc95ff3 100644 > --- a/drivers/gpu/drm/nouveau/dispnv04/dac.c > +++ b/drivers/gpu/drm/nouveau/dispnv04/dac.c > @@ -428,7 +428,7 @@ void nv04_dac_update_dacclk(struct drm_encoder *encoder, bool enable) > struct drm_device *dev = encoder->dev; > struct dcb_output *dcb = nouveau_encoder(encoder)->dcb; > > - if (nv_gf4_disp_arch(dev)) { > + if (nv_gf4_disp_arch(dev) && ffs(dcb->or)) { > uint32_t *dac_users = &nv04_display(dev)->dac_users[ffs(dcb->or) - 1]; > int dacclk_off = NV_PRAMDAC_DACCLK + nv04_dac_output_offset(encoder); > uint32_t dacclk = NVReadRAMDAC(dev, 0, dacclk_off); > @@ -453,7 +453,7 @@ bool nv04_dac_in_use(struct drm_encoder *encoder) > struct drm_device *dev = encoder->dev; > struct dcb_output *dcb = nouveau_encoder(encoder)->dcb; > > - return nv_gf4_disp_arch(encoder->dev) && > + return nv_gf4_disp_arch(encoder->dev) && ffs(dcb->or) && > (nv04_display(dev)->dac_users[ffs(dcb->or) - 1] & ~(1 << dcb->index)); > } >
Lyude Paul
2024-Apr-05 20:05 UTC
[PATCH] drm: nv04: Add check to avoid out of bounds access
On Fri, 2024-04-05 at 17:53 +0200, Danilo Krummrich wrote:> On 3/31/24 08:45, Mikhail Kobuk wrote: > > Output Resource (dcb->or) value is not guaranteed to be non-zero > > (i.e. > > in drivers/gpu/drm/nouveau/nouveau_bios.c, in > > 'fabricate_dcb_encoder_table()' > > 'dcb->or' is assigned value '0' in call to > > 'fabricate_dcb_output()'). > > I don't really know much about the semantics of this code. > > Looking at fabricate_dcb_output() though I wonder if the intention > was to assign > BIT(or) to entry->or. > > @Lyude, can you help here?This code is definitely a bit before my time as well - but I think you're completely correct. Especially considering this bit I found in nouveau_bios.h: enum nouveau_or { DCB_OUTPUT_A = (1 << 0), DCB_OUTPUT_B = (1 << 1), DCB_OUTPUT_C = (1 << 2) };> > Otherwise, for parsing the DCB entries, it seems that the bound > checks are > happening in olddcb_outp_foreach() [1]. > > [1] > https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/nouveau/nouveau_bios.c#L1331 > > > > > Add check to validate 'dcb->or' before it's used. > > > > Found by Linux Verification Center (linuxtesting.org) with SVACE. > > > > Fixes: 2e5702aff395 ("drm/nouveau: fabricate DCB encoder table for > > iMac G4") > > Signed-off-by: Mikhail Kobuk <m.kobuk at ispras.ru> > > --- > > ? drivers/gpu/drm/nouveau/dispnv04/dac.c | 4 ++-- > > ? 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/gpu/drm/nouveau/dispnv04/dac.c > > b/drivers/gpu/drm/nouveau/dispnv04/dac.c > > index d6b8e0cce2ac..0c8d4fc95ff3 100644 > > --- a/drivers/gpu/drm/nouveau/dispnv04/dac.c > > +++ b/drivers/gpu/drm/nouveau/dispnv04/dac.c > > @@ -428,7 +428,7 @@ void nv04_dac_update_dacclk(struct drm_encoder > > *encoder, bool enable) > > ?? struct drm_device *dev = encoder->dev; > > ?? struct dcb_output *dcb = nouveau_encoder(encoder)->dcb; > > ? > > - if (nv_gf4_disp_arch(dev)) { > > + if (nv_gf4_disp_arch(dev) && ffs(dcb->or)) { > > ?? uint32_t *dac_users = &nv04_display(dev)- > > >dac_users[ffs(dcb->or) - 1]; > > ?? int dacclk_off = NV_PRAMDAC_DACCLK + > > nv04_dac_output_offset(encoder); > > ?? uint32_t dacclk = NVReadRAMDAC(dev, 0, > > dacclk_off); > > @@ -453,7 +453,7 @@ bool nv04_dac_in_use(struct drm_encoder > > *encoder) > > ?? struct drm_device *dev = encoder->dev; > > ?? struct dcb_output *dcb = nouveau_encoder(encoder)->dcb; > > ? > > - return nv_gf4_disp_arch(encoder->dev) && > > + return nv_gf4_disp_arch(encoder->dev) && ffs(dcb->or) && > > ?? (nv04_display(dev)->dac_users[ffs(dcb->or) - 1] & > > ~(1 << dcb->index)); > > ? } > > ? >-- Cheers, Lyude Paul (she/her) Software Engineer at Red Hat