Handling argc==0 in the kernel [LWN.net]

Handling argc==0 in the kernel

Posted Jan 30, 2022 21:48 UTC (Sun) by developer122 (guest, #152928)
In reply to: Handling argc==0 in the kernel by floppus
Parent article: Handling argc==0 in the kernel

I think changing argc from 0 to 1 and adding an empty string will probably trip up legitimate programs. If argc is 0, then they may handle that by not checking argv and all is well. If argc is one, then they may expect a valid entry in argv[0]. It's still not great to require a valid name in argv[0], but regardless of what vulnerabilities may exist already I can see this causing more breakage to programs that attempt to handle argc==0 correctly.

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Handling argc==0 in the kernel

Posted Feb 1, 2022 1:37 UTC (Tue) by NYKevin (subscriber, #129325) [Link]

As I explained in another comment, the caller can set argv[0] to any string it wishes, and a setuid program must not trust the caller (because the caller is unprivileged). So all setuid programs *must* behave correctly for invalid or "wrong" argv[0]. If they don't, then that's a separate vulnerability which must be fixed regardless of what the kernel does in the argc == 0 case. By coalescing the two cases into one case, you halve the number of potential vulnerabilities that application writers need to worry about.