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usercopy: remove page-spanning test for now

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A custom allocator without __GFP_COMP that copies to userspace has been
found in vmw_execbuf_process[1], so this disables the page-span checker
by placing it behind a CONFIG for future work where such things can be
tracked down later.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1373326

Reported-by: Vinson Lee <vlee@freedesktop.org>
Fixes: f5509cc18d ("mm: Hardened usercopy")
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook
2016-09-07 09:54:34 -07:00
parent a85d6b8242
commit 8e1f74ea02
2 changed files with 46 additions and 26 deletions
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11
security/Kconfig
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@@ -147,6 +147,17 @@ config HARDENED_USERCOPY
or are part of the kernel text. This kills entire classes
of heap overflow exploits and similar kernel memory exposures.
config HARDENED_USERCOPY_PAGESPAN
bool "Refuse to copy allocations that span multiple pages"
depends on HARDENED_USERCOPY
depends on !COMPILE_TEST
help
When a multi-page allocation is done without __GFP_COMP,
hardened usercopy will reject attempts to copy it. There are,
however, several cases of this in the kernel that have not all
been removed. This config is intended to be used only while
trying to find such users.
source security/selinux/Kconfig
source security/smack/Kconfig
source security/tomoyo/Kconfig