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... 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",