Messages in this thread | | | From | Sergey Senozhatsky <> | Date | Tue, 19 Feb 2019 23:15:16 +0900 | Subject | Re: [PATCH v6 8/9] vsprintf: Prevent crash when dereferencing invalid pointers |
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On (02/19/19 15:49), Andy Shevchenko wrote: > > On (02/19/19 13:02), Andy Shevchenko wrote: > > [..] > > > And if it's not? You will get in either case incomplete information, > > > but at least with "(e" (or even "(") you might get a clue that it > > > errornous conditions. > > > > The thing I'm signaling here is that in some cases we still can > > crash the kernel; with the difference that invalid dereference > > can now be a memory corruption. Just saying. > > Wouldn't that mean that the culprit in the caller, not in the callee? > > (As far as I got your another example with badly called sprintf() which may > overwrite stack, etc).
ipv4 printout case does not look like a caller bug to me: we expect a 15 bytes ipv4 address, allocate a 16 bytes buffer, sprintf() voluntarily writes 18 bytes. This error reporting is a bit of a dangerous practice; next year someone might add another specifier and another
return string(buf, end, "(this data does not look right)", spec);
We probably would want to do something about it. For instance, mandating that "(error)" string cannot be larger than 8 bytes can be a good starting point.
-ss
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