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[PW_SID:1080440] riscv: lib: Fix ZBB strnlen reading past count boundary #1756

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[PW_SID:1080440] riscv: lib: Fix ZBB strnlen reading past count boundary #1756

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10 changes: 9 additions & 1 deletion arch/riscv/lib/strnlen.S
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Original file line number Diff line number Diff line change
Expand Up @@ -83,8 +83,13 @@ strnlen_zbb:
sub t3, t3, t2
slli t2, t2, 3

/* Aligned boundary. */
/*
* Aligned boundary. Use the address of the last valid byte
* (s + count - 1) to avoid loading a word past the count
* boundary in the loop below. count == 0 is handled above.
*/
add t4, a0, a1
addi t4, t4, -1
andi t4, t4, -SZREG

/* Get the first word. */
Expand Down Expand Up @@ -120,6 +125,9 @@ strnlen_zbb:

bgtu t3, a0, 2f

/* All remaining bytes are in the first word, no loop needed. */
bgeu t0, t4, 2f

/* Prepare for the word comparison loop. */
addi t2, t0, SZREG
li t3, -1
Expand Down
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