| Message ID | 20210402233702.3291792-3-seanjc@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | ccp: KVM: SVM: Use stack for SEV command buffers | expand |
On 4/2/21 6:36 PM, Sean Christopherson wrote: > WARN on and reject SEV commands that provide a valid data pointer, but do > not have a known, non-zero length. And conversely, reject commands that > take a command buffer but none is provided. > > Aside from sanity checking intput, disallowing a non-null pointer without s/intput/input/ > a non-zero size will allow a future patch to cleanly handle vmalloc'd > data by copying the data to an internal __pa() friendly buffer. > > Note, this also effectively prevents callers from using commands that > have a non-zero length and are not known to the kernel. This is not an > explicit goal, but arguably the side effect is a good thing from the > kernel's perspective. > > Cc: Brijesh Singh <brijesh.singh@amd.com> > Cc: Borislav Petkov <bp@suse.de> > Cc: Tom Lendacky <thomas.lendacky@amd.com> > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > drivers/crypto/ccp/sev-dev.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c > index 6556d220713b..4c513318f16a 100644 > --- a/drivers/crypto/ccp/sev-dev.c > +++ b/drivers/crypto/ccp/sev-dev.c > @@ -141,6 +141,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret) > struct sev_device *sev; > unsigned int phys_lsb, phys_msb; > unsigned int reg, ret = 0; > + int buf_len; > > if (!psp || !psp->sev_data) > return -ENODEV; > @@ -150,7 +151,11 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret) > > sev = psp->sev_data; > > - if (data && WARN_ON_ONCE(is_vmalloc_addr(data))) > + buf_len = sev_cmd_buffer_len(cmd); > + if (WARN_ON_ONCE(!!data != !!buf_len)) Seems a bit confusing to me. Can this just be: if (WARN_ON_ONCE(data && !buf_len)) Or is this also trying to catch the case where buf_len is non-zero but data is NULL? Thanks, Tom > + return -EINVAL; > + > + if (WARN_ON_ONCE(data && is_vmalloc_addr(data))) > return -EINVAL; > > /* Get the physical address of the command buffer */ > @@ -161,7 +166,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret) > cmd, phys_msb, phys_lsb, psp_timeout); > > print_hex_dump_debug("(in): ", DUMP_PREFIX_OFFSET, 16, 2, data, > - sev_cmd_buffer_len(cmd), false); > + buf_len, false); > > iowrite32(phys_lsb, sev->io_regs + sev->vdata->cmdbuff_addr_lo_reg); > iowrite32(phys_msb, sev->io_regs + sev->vdata->cmdbuff_addr_hi_reg); > @@ -197,7 +202,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret) > } > > print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data, > - sev_cmd_buffer_len(cmd), false); > + buf_len, false); > > return ret; > } >
On Mon, Apr 05, 2021, Tom Lendacky wrote: > On 4/2/21 6:36 PM, Sean Christopherson wrote: > > diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c > > index 6556d220713b..4c513318f16a 100644 > > --- a/drivers/crypto/ccp/sev-dev.c > > +++ b/drivers/crypto/ccp/sev-dev.c > > @@ -141,6 +141,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret) > > struct sev_device *sev; > > unsigned int phys_lsb, phys_msb; > > unsigned int reg, ret = 0; > > + int buf_len; > > > > if (!psp || !psp->sev_data) > > return -ENODEV; > > @@ -150,7 +151,11 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret) > > > > sev = psp->sev_data; > > > > - if (data && WARN_ON_ONCE(is_vmalloc_addr(data))) > > + buf_len = sev_cmd_buffer_len(cmd); > > + if (WARN_ON_ONCE(!!data != !!buf_len)) > > Seems a bit confusing to me. Can this just be: > > if (WARN_ON_ONCE(data && !buf_len)) Or as Christophe pointed out, "!data != !buf_len". > Or is this also trying to catch the case where buf_len is non-zero but > data is NULL? Ya. It's not necessary to detect "buf_len && !data", but it doesn't incur additional cost. Is there a reason _not_ to disallow that?
On 4/5/21 11:33 AM, Sean Christopherson wrote: > On Mon, Apr 05, 2021, Tom Lendacky wrote: >> On 4/2/21 6:36 PM, Sean Christopherson wrote: >>> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c >>> index 6556d220713b..4c513318f16a 100644 >>> --- a/drivers/crypto/ccp/sev-dev.c >>> +++ b/drivers/crypto/ccp/sev-dev.c >>> @@ -141,6 +141,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret) >>> struct sev_device *sev; >>> unsigned int phys_lsb, phys_msb; >>> unsigned int reg, ret = 0; >>> + int buf_len; >>> >>> if (!psp || !psp->sev_data) >>> return -ENODEV; >>> @@ -150,7 +151,11 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret) >>> >>> sev = psp->sev_data; >>> >>> - if (data && WARN_ON_ONCE(is_vmalloc_addr(data))) >>> + buf_len = sev_cmd_buffer_len(cmd); >>> + if (WARN_ON_ONCE(!!data != !!buf_len)) >> >> Seems a bit confusing to me. Can this just be: >> >> if (WARN_ON_ONCE(data && !buf_len)) > > Or as Christophe pointed out, "!data != !buf_len". > >> Or is this also trying to catch the case where buf_len is non-zero but >> data is NULL? > > Ya. It's not necessary to detect "buf_len && !data", but it doesn't incur > additional cost. Is there a reason _not_ to disallow that? Nope, no reason. I was just trying to process all the not signs :) Thanks, Tom >
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c index 6556d220713b..4c513318f16a 100644 --- a/drivers/crypto/ccp/sev-dev.c +++ b/drivers/crypto/ccp/sev-dev.c @@ -141,6 +141,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret) struct sev_device *sev; unsigned int phys_lsb, phys_msb; unsigned int reg, ret = 0; + int buf_len; if (!psp || !psp->sev_data) return -ENODEV; @@ -150,7 +151,11 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret) sev = psp->sev_data; - if (data && WARN_ON_ONCE(is_vmalloc_addr(data))) + buf_len = sev_cmd_buffer_len(cmd); + if (WARN_ON_ONCE(!!data != !!buf_len)) + return -EINVAL; + + if (WARN_ON_ONCE(data && is_vmalloc_addr(data))) return -EINVAL; /* Get the physical address of the command buffer */ @@ -161,7 +166,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret) cmd, phys_msb, phys_lsb, psp_timeout); print_hex_dump_debug("(in): ", DUMP_PREFIX_OFFSET, 16, 2, data, - sev_cmd_buffer_len(cmd), false); + buf_len, false); iowrite32(phys_lsb, sev->io_regs + sev->vdata->cmdbuff_addr_lo_reg); iowrite32(phys_msb, sev->io_regs + sev->vdata->cmdbuff_addr_hi_reg); @@ -197,7 +202,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret) } print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data, - sev_cmd_buffer_len(cmd), false); + buf_len, false); return ret; }
WARN on and reject SEV commands that provide a valid data pointer, but do not have a known, non-zero length. And conversely, reject commands that take a command buffer but none is provided. Aside from sanity checking intput, disallowing a non-null pointer without a non-zero size will allow a future patch to cleanly handle vmalloc'd data by copying the data to an internal __pa() friendly buffer. Note, this also effectively prevents callers from using commands that have a non-zero length and are not known to the kernel. This is not an explicit goal, but arguably the side effect is a good thing from the kernel's perspective. Cc: Brijesh Singh <brijesh.singh@amd.com> Cc: Borislav Petkov <bp@suse.de> Cc: Tom Lendacky <thomas.lendacky@amd.com> Signed-off-by: Sean Christopherson <seanjc@google.com> --- drivers/crypto/ccp/sev-dev.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)