janvcelak created this revision.
janvcelak added a reviewer: dcoughlin.
Herald added subscribers: cfe-commits, Charusso, dkrupp, donat.nagy, Szelethus,
mikhail.ramalho, a.sidorin, szepet, baloghadamsoftware, xazax.hun.
Herald added a project: clang.
`execve` is missing in the list of functions that are allowed after `vfork()`.
As a result, clang analyzer reports the following false positive:
#include <unistd.h>
int main(int argc, char *argv[])
{
char *a[] = {"true", NULL};
char *e[] = {NULL};
if (vfork() == 0) {
execve("/bin/true", a, e);
_exit(1);
}
return 0;
}
$ scan-build clang -Wall -c repro.c
scan-build: Using '/usr/bin/clang-9' for static analysis
repro.c:7:6: warning: Call to function 'vfork' is insecure as it can lead to
denial of service situations in the parent process. Replace calls to vfork with
calls to the safer 'posix_spawn' function
if (vfork() == 0) {
^~~~~
repro.c:8:3: warning: This function call is prohibited after a successful
vfork
execve("/bin/true", a, e);
^~~~~~~~~~~~~~~~~~~~~~~~~
2 warnings generated.
scan-build: 2 bugs found.
scan-build: Run 'scan-view /tmp/scan-build-2020-01-29-162705-3770808-1' to
examine bug reports.
The list of exec functions in the code is take from the `exec(3)` man page
which are just a fronted for `execve(2)`. Quoting the manual page:
> The exec() family of functions replaces the current process image with a new
> process image. The functions escribed in this manual page are front-ends for
> execve(2). (See the manual page for execve(2) for further details about the
> replacement of the current process image.)
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D73629
Files:
clang/lib/StaticAnalyzer/Checkers/VforkChecker.cpp
Index: clang/lib/StaticAnalyzer/Checkers/VforkChecker.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Checkers/VforkChecker.cpp
+++ clang/lib/StaticAnalyzer/Checkers/VforkChecker.cpp
@@ -106,6 +106,7 @@
"execv",
"execvp",
"execvpe",
+ "execve",
nullptr
};
Index: clang/lib/StaticAnalyzer/Checkers/VforkChecker.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Checkers/VforkChecker.cpp
+++ clang/lib/StaticAnalyzer/Checkers/VforkChecker.cpp
@@ -106,6 +106,7 @@
"execv",
"execvp",
"execvpe",
+ "execve",
nullptr
};
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