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Subject[PATCH net-next v2 7/7] net: ipa: avoid field overflow
Date
It's possible that the length passed to ipa_header_size_encoded()
is larger than what can be represented by the HDR_LEN field alone
(starting with IPA v4.5). If we attempted that, u32_encode_bits()
would trigger a build-time error.

Avoid this problem by masking off high-order bits of the value
encoded as the lower portion of the header length.

The same sort of problem exists in ipa_metadata_offset_encoded(),
so implement the same fix there.

Signed-off-by: Alex Elder <elder@linaro.org>
---
drivers/net/ipa/ipa_reg.h | 22 ++++++++++++++--------
1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ipa/ipa_reg.h b/drivers/net/ipa/ipa_reg.h
index e6b0827a244ec..732e691e9aa62 100644
--- a/drivers/net/ipa/ipa_reg.h
+++ b/drivers/net/ipa/ipa_reg.h
@@ -408,15 +408,18 @@ enum ipa_cs_offload_en {
static inline u32 ipa_header_size_encoded(enum ipa_version version,
u32 header_size)
{
+ u32 size = header_size & field_mask(HDR_LEN_FMASK);
u32 val;

- val = u32_encode_bits(header_size, HDR_LEN_FMASK);
- if (version < IPA_VERSION_4_5)
+ val = u32_encode_bits(size, HDR_LEN_FMASK);
+ if (version < IPA_VERSION_4_5) {
+ /* ipa_assert(header_size == size); */
return val;
+ }

/* IPA v4.5 adds a few more most-significant bits */
- header_size >>= hweight32(HDR_LEN_FMASK);
- val |= u32_encode_bits(header_size, HDR_LEN_MSB_FMASK);
+ size = header_size >> hweight32(HDR_LEN_FMASK);
+ val |= u32_encode_bits(size, HDR_LEN_MSB_FMASK);

return val;
}
@@ -425,15 +428,18 @@ static inline u32 ipa_header_size_encoded(enum ipa_version version,
static inline u32 ipa_metadata_offset_encoded(enum ipa_version version,
u32 offset)
{
+ u32 off = offset & field_mask(HDR_OFST_METADATA_FMASK);
u32 val;

- val = u32_encode_bits(offset, HDR_OFST_METADATA_FMASK);
- if (version < IPA_VERSION_4_5)
+ val = u32_encode_bits(off, HDR_OFST_METADATA_FMASK);
+ if (version < IPA_VERSION_4_5) {
+ /* ipa_assert(offset == off); */
return val;
+ }

/* IPA v4.5 adds a few more most-significant bits */
- offset >>= hweight32(HDR_OFST_METADATA_FMASK);
- val |= u32_encode_bits(offset, HDR_OFST_METADATA_MSB_FMASK);
+ off = offset >> hweight32(HDR_OFST_METADATA_FMASK);
+ val |= u32_encode_bits(off, HDR_OFST_METADATA_MSB_FMASK);

return val;
}
--
2.20.1
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