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U2FsdGVkX1++oqFZbSRRooF//ULvNqDd3LJMWwENge8BrOGucUGCpjgLbNsNkGhLLX3B4pz6Z9I6uVmKjKDrMVQuVjP0igHr+vB+rFpQd+fmZmBLX/INhfrEW6phUU4O4khDkqqVDo+qxwDypnIBKOW/alQalBuqOq0B3AOarm5vm3RF/KEnSrQzxjohoLyBbl5Cgc+P3d45ALU5yKpZhPhSmj7Ty1WojYnjxPwpBWkFkcjbvfBKTCVwr30pGIN4k8zueu6/t9s1NPg5YlvMkPf17KOnVYcB/dNuNfvqTwj77TeWPstv/8PYxJ3UlDH9KvpcU2k78y+g6h95cAF7V7DHu6TyNYEIFMP1nSGTzoP83xwhmX5kVOpH2ktPyExQEcUpU4JaXYcS4fmGuZwSIUSrNs+5FqykXKXHgKUtCaz4ZVzmLaJX+7pEehKAUbfo1zwDPeGmcyDTmDD7qW/rnCj11HePvr4DtUFaJAv08gmtglI54PaUrUUrU4HZW3elaitauE30hHqPjpkkDeRpX8tUTrZZvZi4cS718jX/U1vviBYrQJxI3uXKdfhtE0pnmlwYtwQA86HJX2dBH/wwUGuMDxO1H2CGrGCjfmEFa4L4MK3h0DnyN6M16wJaxRGjRVPEhKYk+h+CcUUZKcs6yDWkVs9AHjE7t97Snd+7tujkVgNa7NjDgXQqIdBMSomwnmJhnLy7LASMfRuI9e/A6F60jtKBnvHX4oCaPALusq8Wo7EHyZFURAyTTpgNhQU6Ra6tmfxMDNuGTsVw8io0/XfcUgXnVQbi2dOO5tv/yvjA4Oq1GwyJJhkFcr16FFJwqNAzMSOe6LmdITDWMiAzgquV0ZPItV49+6y4hOhV6x8SpvP4gjvnQfMxgrH7pGm5wKn6a2s6YxQUrdvrK7gaL2CwRNODO2h8oogpBtA5TUBq3wfwCk1oWnjuNKwNs6hA3eYd0/yPik17M9PTyV9 MnjMLq0J 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has the potential to overflow, leading to undefined > > behavior according to the C standard. However, both GCC and Clang > > compilers may eliminate this overflow check based on the assumption > > that there will be no undefined behavior. Although the Linux kernel > > disables these optimizations by using the -fno-strict-overflow option, > > there is still a risk if the compilers make mistakes in the future. > > So we're adding code to handle eventual future compiler bugs? That sounds > wrong, but maybe I misunderstood the problem you are trying to solve? Like David, adding a fix for a potential future compiler bug sounds wrong. I have no problem with restructuring code to make it more immune to potential issues. However, it appears there are several places throughout the kernel that perform similar checks. For example: do_mmap() /* offset overflow? */ if ((pgoff + (len >> PAGE_SHIFT)) < pgoff) return -EOVERFLOW; expand_upwards() /* Enforce stack_guard_gap */ gap_addr = address + stack_guard_gap; /* Guard against overflow */ if (gap_addr < address || gap_addr > TASK_SIZE) gap_addr = TASK_SIZE; do_madvise() end = start + len; if (end < start) return -EINVAL; I am not suggesting that these all be changed. The question of a real issue still remains. However, if this is a real issue it would make more sense to look for and change all such checks rather than one single occurrence. -- Mike Kravetz