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riscv/futex: sign extend compare value in atomic cmpxchg

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Make sure the compare value in the lr/sc loop is sign extended to match
what lr.w does.  Fortunately, due to the compiler keeping the register
contents sign extended anyway the lack of the explicit extension didn't
result in wrong code so far, but this cannot be relied upon.

Fixes: b90edb3301 ("RISC-V: Add futex support.")
Signed-off-by: Andreas Schwab <schwab@suse.de>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/mvmfrkv2vhz.fsf@suse.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Andreas Schwab 2025-02-03 11:06:00 +01:00 • committed by Palmer Dabbelt
parent 1898300abf
commit 599c44cd21
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1 changed files with 1 additions and 1 deletions
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arch/riscv/include/asm/futex.h
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@ -93,7 +93,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
_ASM_EXTABLE_UACCESS_ERR(1b, 3b, %[r]) \
_ASM_EXTABLE_UACCESS_ERR(2b, 3b, %[r]) \
: [r] "+r" (ret), [v] "=&r" (val), [u] "+m" (*uaddr), [t] "=&r" (tmp)
: [ov] "Jr" (oldval), [nv] "Jr" (newval)
: [ov] "Jr" ((long)(int)oldval), [nv] "Jr" (newval)
: "memory");
__disable_user_access();