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authorWill Deacon <will.deacon@arm.com>2019-01-19 21:56:05 +0000
committerLinus Torvalds <torvalds@linux-foundation.org>2019-01-20 15:33:22 +1200
commit6e693b3ffecb0b478c7050b44a4842854154f715 (patch)
tree3e46191be19e74dc996c422c03b22aa7818c0870
parentb0f3e768a89bbc72195023c3db1db45c40e5b70c (diff)
download96b-common-6e693b3ffecb0b478c7050b44a4842854154f715.tar.gz
x86: uaccess: Inhibit speculation past access_ok() in user_access_begin()
Commit 594cc251fdd0 ("make 'user_access_begin()' do 'access_ok()'") makes the access_ok() check part of the user_access_begin() preceding a series of 'unsafe' accesses. This has the desirable effect of ensuring that all 'unsafe' accesses have been range-checked, without having to pick through all of the callsites to verify whether the appropriate checking has been made. However, the consolidated range check does not inhibit speculation, so it is still up to the caller to ensure that they are not susceptible to any speculative side-channel attacks for user addresses that ultimately fail the access_ok() check. This is an oversight, so use __uaccess_begin_nospec() to ensure that speculation is inhibited until the access_ok() check has passed. Reported-by: Julien Thierry <julien.thierry@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--arch/x86/include/asm/uaccess.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index a77445d1b034..780f2b42c8ef 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -711,7 +711,7 @@ static __must_check inline bool user_access_begin(const void __user *ptr, size_t
{
if (unlikely(!access_ok(ptr,len)))
return 0;
- __uaccess_begin();
+ __uaccess_begin_nospec();
return 1;
}
#define user_access_begin(a,b) user_access_begin(a,b)