Messages in this thread | | | Date | Mon, 04 May 2020 19:32:41 -0700 | From | bbhatt@codeauro ... | Subject | Re: [PATCH v4 8/8] bus: mhi: core: Ensure non-zero session or sequence ID values are used |
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On 2020-05-04 07:33, Jeffrey Hugo wrote: > On 5/1/2020 8:32 PM, Bhaumik Bhatt wrote: >> While writing any sequence or session identifiers, it is possible that >> the host could write a zero value, whereas only non-zero values should >> be supported writes to those registers. Ensure that the host does not >> write a non-zero value for them and also log them in debug messages. >> >> Suggested-by: Jeffrey Hugo <jhugo@codeaurora.org> >> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org> >> --- >> drivers/bus/mhi/core/boot.c | 15 +++++++-------- >> drivers/bus/mhi/core/internal.h | 1 + >> 2 files changed, 8 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/bus/mhi/core/boot.c b/drivers/bus/mhi/core/boot.c >> index e5fcde1..9fe9c59 100644 >> --- a/drivers/bus/mhi/core/boot.c >> +++ b/drivers/bus/mhi/core/boot.c >> @@ -43,10 +43,7 @@ void mhi_rddm_prepare(struct mhi_controller >> *mhi_cntrl, >> lower_32_bits(mhi_buf->dma_addr)); >> mhi_write_reg(mhi_cntrl, base, BHIE_RXVECSIZE_OFFS, >> mhi_buf->len); >> - sequence_id = prandom_u32() & BHIE_RXVECSTATUS_SEQNUM_BMSK; >> - >> - if (unlikely(!sequence_id)) >> - sequence_id = 1; >> + sequence_id = (MHI_RANDOM_U32_NONZERO & >> BHIE_RXVECSTATUS_SEQNUM_BMSK); > > I don't think this math works. For example, if MHI_RANDOM_U32_NONZERO > is 0x0FF0, and BHIE_RXVECSTATUS_SEQNUM_BMSK is 0xF, then sequence_id > will end up being 0.
In this case, SEQNUM BMSK is set to 0x3FFFFFFF so this change will still work as we only supplied a non-zero number macro to AND with the mask. However, I agree that may not be the case always that we would know the bitmask in advance so it is better to fix it for good.
Thanks for the catch! I have updated the change to have the macro take the bitmask as a parameter and output a non-zero value.
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