[compiler-rt] [dfsan] Make sprintf interceptor compatible with glibc 2.37+ and musl (PR #78363)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Fangrui Song (MaskRay)

<details>
<summary>Changes</summary>

snprintf interceptors call `format_buffer` with `size==~0ul`, which
may eventually lead to `snprintf(s, n, "Hello world!")` where `s+n`
wraps around. Since glibc 2.37 (https://sourceware.org/PR31251), the
snprintf call does not write the last char. musl snprintf returns -1
with EOVERFLOW when `n > INT_MAX`.

Change `size` to INT_MAX to work with glibc 2.37+ and musl.
snprintf interceptors are not changed. It's user responsibility to not
cause a compatibility issue with libc implementations.

Fix #<!-- -->60678


---
Full diff: https://github.com/llvm/llvm-project/pull/78363.diff


3 Files Affected:

- (modified) compiler-rt/lib/dfsan/dfsan_custom.cpp (+3-3) 
- (modified) compiler-rt/test/dfsan/custom.cpp (-3) 
- (modified) compiler-rt/test/dfsan/release_shadow_space.c (-3) 


``````````diff
diff --git a/compiler-rt/lib/dfsan/dfsan_custom.cpp b/compiler-rt/lib/dfsan/dfsan_custom.cpp
index 05b48fd0525e335..c5c14a2d1b0eb43 100644
--- a/compiler-rt/lib/dfsan/dfsan_custom.cpp
+++ b/compiler-rt/lib/dfsan/dfsan_custom.cpp
@@ -2792,7 +2792,7 @@ int __dfsw_sprintf(char *str, const char *format, dfsan_label str_label,
   va_list ap;
   va_start(ap, ret_label);
 
-  int ret = format_buffer(str, ~0ul, format, va_labels, ret_label, nullptr,
+  int ret = format_buffer(str, INT32_MAX, format, va_labels, ret_label, nullptr,
                           nullptr, ap);
   va_end(ap);
   return ret;
@@ -2806,8 +2806,8 @@ int __dfso_sprintf(char *str, const char *format, dfsan_label str_label,
                    dfsan_origin *ret_origin, ...) {
   va_list ap;
   va_start(ap, ret_origin);
-  int ret = format_buffer(str, ~0ul, format, va_labels, ret_label, va_origins,
-                          ret_origin, ap);
+  int ret = format_buffer(str, INT32_MAX, format, va_labels, ret_label,
+                          va_origins, ret_origin, ap);
   va_end(ap);
   return ret;
 }
diff --git a/compiler-rt/test/dfsan/custom.cpp b/compiler-rt/test/dfsan/custom.cpp
index 56e66fd5069a682..2ebeb1e4519782d 100644
--- a/compiler-rt/test/dfsan/custom.cpp
+++ b/compiler-rt/test/dfsan/custom.cpp
@@ -1,6 +1,3 @@
-// https://github.com/llvm/llvm-project/issues/60678
-// XFAIL: glibc-2.37
-
 // RUN: %clang_dfsan %s -o %t && DFSAN_OPTIONS="strict_data_dependencies=0" %run %t
 // RUN: %clang_dfsan -DSTRICT_DATA_DEPENDENCIES %s -o %t && %run %t
 // RUN: %clang_dfsan -DORIGIN_TRACKING -mllvm -dfsan-track-origins=1 -mllvm -dfsan-combine-pointer-labels-on-load=false -DSTRICT_DATA_DEPENDENCIES %s -o %t && %run %t
diff --git a/compiler-rt/test/dfsan/release_shadow_space.c b/compiler-rt/test/dfsan/release_shadow_space.c
index 9492f2ad7728ccf..675640a1c296da2 100644
--- a/compiler-rt/test/dfsan/release_shadow_space.c
+++ b/compiler-rt/test/dfsan/release_shadow_space.c
@@ -1,6 +1,3 @@
-// https://github.com/llvm/llvm-project/issues/60678
-// XFAIL: glibc-2.37
-
 // DFSAN_OPTIONS=no_huge_pages_for_shadow=false RUN: %clang_dfsan %s -o %t && %run %t
 // DFSAN_OPTIONS=no_huge_pages_for_shadow=true RUN: %clang_dfsan %s -o %t && %run %t
 // DFSAN_OPTIONS=no_huge_pages_for_shadow=false RUN: %clang_dfsan %s -DORIGIN_TRACKING -mllvm -dfsan-track-origins=1 -o %t && %run %t

``````````

</details>


https://github.com/llvm/llvm-project/pull/78363