Sean Christopherson <seanjc@xxxxxxxxxx> writes: > On Wed, Mar 31, 2021, Yang Li wrote: >> Using __set_bit() to set a bit in an integer is not a good idea, since >> the function expects an unsigned long as argument, which can be 64bit wide. >> Coverity reports this problem as >> >> High:Out-of-bounds access(INCOMPATIBLE_CAST) >> CWE119: Out-of-bounds access to a scalar >> Pointer "&vcpu->arch.regs_avail" points to an object whose effective >> type is "unsigned int" (32 bits, unsigned) but is dereferenced as a >> wider "unsigned long" (64 bits, unsigned). This may lead to memory >> corruption. >> >> /home/heyuan.shy/git-repo/linux/arch/x86/kvm/kvm_cache_regs.h: >> kvm_register_is_available >> >> Just use BIT instead. > > Meh, we're hosed either way. Using BIT() will either result in undefined > behavior due to SHL shifting beyond the size of a u64, or setting random bits > if the truncated shift ends up being less than 63. > A stupid question: why can't we just make 'regs_avail'/'regs_dirty' 'unsigned long' and drop a bunch of '(unsigned long *)' casts? -- Vitaly
