Messages in this thread |  | | | From | (H. Peter Anvin) | | Subject | Re: copy_from_user() fix | | Date | 25 Aug 1998 21:57:03 GMT |
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Followup to: <19980825133811.20709.qmail@ohse.de> By author: uwe@ohse.de (Uwe Ohse) In newsgroup: linux.dev.kernel > > In <6rtm8e$9bc$1@palladium.transmeta.com> H. Peter Anvin wrote: > > >So, what happens if the libc/kernel interface is changed? You're > >screwed, because your code is broken. > > You'll screw up other people, too. > > Please tell me another way to check if some memory range if safe > to be written to if this doesn't work anymore: > > int fd=open("/dev/zero",O_RDONLY); > ... > if (read(fd,mem,size)!=(ssize_t) size) > return -1; > /* ok */ > return 0; > > Please don't tell me to set up signal handlers, i've done that before > and will not do it again for this purpose. More so inside a library > which is supposed to (a) not crash and (b) be reasonable fast. > > I'm actually using this feature in a logging library of mime, > and i will _really_ hate it if this doesn't work anymore. >
This is broken. If you run zlibc, for example, read() is implemented as a library function. You have no guarantee that that works; and it may break for reasons that you don't know.
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