| From | Sasha Levin <> | Subject | [PATCH AUTOSEL 5.4 167/350] ubsan, x86: Annotate and allow __ubsan_handle_shift_out_of_bounds() in uaccess regions | Date | Tue, 10 Dec 2019 16:04:32 -0500 |
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From: Peter Zijlstra <peterz@infradead.org>
[ Upstream commit 9a50dcaf0416a43e1fe411dc61a99c8333c90119 ]
The new check_zeroed_user() function uses variable shifts inside of a user_access_begin()/user_access_end() section and that results in GCC emitting __ubsan_handle_shift_out_of_bounds() calls, even though through value range analysis it would be able to see that the UB in question is impossible.
Annotate and whitelist this UBSAN function; continued use of user_access_begin()/user_access_end() will undoubtedly result in further uses of function.
Reported-by: Randy Dunlap <rdunlap@infradead.org> Tested-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Randy Dunlap <rdunlap@infradead.org> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: cyphar@cyphar.com Cc: keescook@chromium.org Cc: linux@rasmusvillemoes.dk Fixes: f5a1a536fa14 ("lib: introduce copy_struct_from_user() helper") Link: https://lkml.kernel.org/r/20191021131149.GA19358@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> --- lib/ubsan.c | 5 ++++- tools/objtool/check.c | 1 + 2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/lib/ubsan.c b/lib/ubsan.c index e7d31735950de..0c4681118fcd2 100644 --- a/lib/ubsan.c +++ b/lib/ubsan.c @@ -374,9 +374,10 @@ void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data, struct type_descriptor *lhs_type = data->lhs_type; char rhs_str[VALUE_LENGTH]; char lhs_str[VALUE_LENGTH]; + unsigned long ua_flags = user_access_save(); if (suppress_report(&data->location)) - return; + goto out; ubsan_prologue(&data->location, &flags); @@ -402,6 +403,8 @@ void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data, lhs_type->type_name); ubsan_epilogue(&flags); +out: + user_access_restore(ua_flags); } EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds); diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 543c068096b12..4768d91c6d686 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -482,6 +482,7 @@ static const char *uaccess_safe_builtin[] = { "ubsan_type_mismatch_common", "__ubsan_handle_type_mismatch", "__ubsan_handle_type_mismatch_v1", + "__ubsan_handle_shift_out_of_bounds", /* misc */ "csum_partial_copy_generic", "__memcpy_mcsafe", -- 2.20.1
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