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Add fbounds-safety annotations for VP8LBitReader.

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Reasoning:

Analysis of the `VP8LBitReader` struct and its initialization function
`VP8LInitBitReader` confirmed that the `len` member holds the size of
the buffer pointed to by `buf`. Therefore, `__counted_by(len)` was added
to `buf` in the struct definition.

This introduced new errors related to function parameters being treated
as `__single` and the `__counted_by` side-by-side assignment rule:
1. In `VP8LInitBitReader`, the `start` parameter was indexed
   (`start[i]`) but was implicitly `__single`. It was annotated with
   `__counted_by(length)` in both the definition and prototype.
2. `br->buf = start` was moved immediately after `br->len = length`.
3. In `VP8LBitReaderSetBuffer`, the `buf` parameter was assigned to
   `br->buf`, which requires the parameter to also be annotated.
   `__counted_by(len)` was added to the `buf` parameter in the
   definition and `__counted_by(length)` to the `buffer` parameter in
   the prototype.

Bug: 432511821
Change-Id: Ie2d5b7b321fb02e8c6b6d3cbd933d056b1bb82cf
This commit is contained in:
Arman Hasanzadeh
2025-08-12 16:35:56 -07:00
committed by James Zern
parent 2246828be3
commit 19f28b7889
2 changed files with 15 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
src/utils/bit_reader_utils.c
View File

@@ -130,7 +130,8 @@ static const uint32_t kBitMask[VP8L_MAX_NUM_BIT_READ + 1] = {
0x003fff, 0x007fff, 0x00ffff, 0x01ffff, 0x03ffff, 0x07ffff, 0x0fffff,
0x1fffff, 0x3fffff, 0x7fffff, 0xffffff};
void VP8LInitBitReader(VP8LBitReader* const br, const uint8_t* const start,
void VP8LInitBitReader(VP8LBitReader* const br,
const uint8_t* const WEBP_COUNTED_BY(length) start,
size_t length) {
size_t i;
vp8l_val_t value = 0;
@@ -138,6 +139,7 @@ void VP8LInitBitReader(VP8LBitReader* const br, const uint8_t* const start,
assert(start != NULL);
assert(length < 0xfffffff8u); // can't happen with a RIFF chunk.
br->buf = start;
br->len = length;
br->val = 0;
br->bit_pos = 0;
@@ -151,10 +153,10 @@ void VP8LInitBitReader(VP8LBitReader* const br, const uint8_t* const start,
}
br->val = value;
br->pos = length;
br->buf = start;
}
void VP8LBitReaderSetBuffer(VP8LBitReader* const br, const uint8_t* const buf,
void VP8LBitReaderSetBuffer(VP8LBitReader* const br,
const uint8_t* const WEBP_COUNTED_BY(len) buf,
size_t len) {
assert(br != NULL);
assert(buf != NULL);

8
src/utils/bit_reader_utils.h
View File

@@ -147,19 +147,21 @@ typedef uint64_t vp8l_val_t; // right now, this bit-reader can only use 64bit.
typedef struct {
vp8l_val_t val; // pre-fetched bits
const uint8_t* buf; // input byte buffer
const uint8_t* WEBP_COUNTED_BY(len) buf; // input byte buffer
size_t len; // buffer length
size_t pos; // byte position in buf
int bit_pos; // current bit-reading position in val
int eos; // true if a bit was read past the end of buffer
} VP8LBitReader;
void VP8LInitBitReader(VP8LBitReader* const br, const uint8_t* const start,
void VP8LInitBitReader(VP8LBitReader* const br,
const uint8_t* const WEBP_COUNTED_BY(length) start,
size_t length);
// Sets a new data buffer.
void VP8LBitReaderSetBuffer(VP8LBitReader* const br,
const uint8_t* const buffer, size_t length);
const uint8_t* const WEBP_COUNTED_BY(length) buffer,
size_t length);
// Reads the specified number of bits from read buffer.
// Flags an error in case end_of_stream or n_bits is more than the allowed limit