From: David Laight David.Laight@ACULAB.COM
mainline inclusion from mainline-v6.13-rc1 commit 573f45a9f9a47fed4c7957609689b772121b33d7 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IB2BWT CVE: CVE-2024-50102
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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When the size isn't a small constant, __access_ok() will call valid_user_address() with the address after the last byte of the user buffer.
It is valid for a buffer to end with the last valid user address so valid_user_address() must allow accesses to the base of the guard page.
[ This introduces an off-by-one in the other direction for the plain non-sized accesses, but since we have that guard region that is a whole page, those checks "allowing" accesses to that guard region don't really matter. The access will fault anyway, whether to the guard page or if the address has been masked to all ones - Linus ]
Fixes: 86e6b1547b3d0 ("x86: fix user address masking non-canonical speculation issue") Signed-off-by: David Laight david.laight@aculab.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Qi Xi xiqi2@huawei.com --- arch/x86/kernel/cpu/common.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index cbdcdd2956e0..570ecdca404b 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -2447,12 +2447,12 @@ void __init arch_cpu_finalize_init(void) alternative_instructions();
if (IS_ENABLED(CONFIG_X86_64)) { - unsigned long USER_PTR_MAX = TASK_SIZE_MAX-1; + unsigned long USER_PTR_MAX = TASK_SIZE_MAX;
/* * Enable this when LAM is gated on LASS support if (cpu_feature_enabled(X86_FEATURE_LAM)) - USER_PTR_MAX = (1ul << 63) - PAGE_SIZE - 1; + USER_PTR_MAX = (1ul << 63) - PAGE_SIZE; */ runtime_const_init(ptr, USER_PTR_MAX);