examples/io_uring-udp: compute buffer size and offset in size_t#1589
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examples/io_uring-udp: compute buffer size and offset in size_t#1589rootvector2 wants to merge 1 commit into
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buffer_size() and get_buffer() shift by ctx->buf_shift, which comes from the -b option (log2 of the buffer size), but evaluate 1U << buf_shift and idx << buf_shift in 32-bit before widening to size_t / a pointer. For a shift >= 32 that is undefined behavior, and even otherwise the result truncates to 32 bits, so buffer_size() returns a wrong value and get_buffer() forms an out-of-range pointer. Building with -fsanitize=undefined and running with -b 40 reports runtime error: shift exponent 40 is too large for 32-bit type and buffer_size() returns 256 instead of 2^40. Do both shifts in size_t. Signed-off-by: rootvector2 <dxbnaveed.k@gmail.com>
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buffer_size() and get_buffer() take their shift count from the -b option but evaluate the shift in 32-bit before widening, so a large value is undefined behavior and otherwise truncates the result. Do both shifts in size_t. Building with -fsanitize=undefined and running with -b 40 flags the old code (shift exponent 40 too large for 32-bit type), and buffer_size() returns 256 instead of 2^40.