Messages in this thread | | | Subject | Re: [PATCH 1/2] signal: Factor copy_siginfo_to_external32 from copy_siginfo_to_user32 | From | Christophe Leroy <> | Date | Sun, 19 Apr 2020 11:46:55 +0200 |
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Le 19/04/2020 à 10:13, Christoph Hellwig a écrit : > On Sat, Apr 18, 2020 at 06:55:56AM -0500, Eric W. Biederman wrote: >>> Is that really an issue to use that set_fs() in the coredump code ? >> >> Using set_fs() is pretty bad and something that we would like to remove >> from the kernel entirely. The fewer instances of set_fs() we have the >> better. >> >> I forget all of the details but set_fs() is both a type violation and an >> attack point when people are attacking the kernel. The existence of >> set_fs() requires somethings that should be constants to be variables. >> Something about that means that our current code is difficult to protect >> from spectre style vulnerabilities. > > Yes, set_fs requires variable based address checking in the uaccess > routines for architectures with a shared address space, or even entirely > different code for architectures with separate kernel and user address > spaces. My plan is to hopefully kill set_fs in its current form a few > merge windows down the road. We'll probably still need some form of > it to e.g. mark a thread as kernel thread vs also being able to execute > user code, but it will be much ore limited than before, called from very > few places and actually be a no-op for many architectures. >
Oh nice. Some time ago I proposed a patch to change set_fs() to a flip/flop flag based logic, see https://patchwork.ozlabs.org/project/linuxppc-dev/patch/dd2876b808ea38eb7b7f760ecd6ce06096c61fb5.1580295551.git.christophe.leroy@c-s.fr/
But if we manage to get rid of it completely, that's even better.
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