From 39303579ebc44edbb872334595e6979b4cc16e28 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 21 Oct 2019 15:11:49 +0200 Subject: [PATCH] ubsan, x86: Annotate and allow __ubsan_handle_shift_out_of_bounds() in uaccess regions [ 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 Tested-by: Randy Dunlap Signed-off-by: Peter Zijlstra (Intel) Acked-by: Randy Dunlap Acked-by: Christian Brauner Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephen Rothwell Cc: Thomas Gleixner 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 Signed-off-by: Sasha Levin --- 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 e7d31735950d..0c4681118fcd 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 044c9a3cb247..f53d3c515cdc 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -481,6 +481,7 @@ 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",