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fix null pointer derefs

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The code for creating a Passwd from the fields of the raw syscall result
assumed that the syscall would return valid C strings in all non-error
cases. This is not true, and at least one platform (Android) will
populate the fields with null pointers where they are not supported.

To fix this and prevent the error from happening again, this commit
changes `cstr2string(ptr)` to check for a null pointer, and return an
`Option<String>`, with `None` being the null pointer case. While
arguably it should be the caller's job to check for a null pointer
before calling (since the safety precondition is that the pointer is to
a valid C string), relying on the type checker to force remembering this
edge case is safer in the long run.
This commit is contained in:
Justin Tracey 2022-02-17 00:58:34 -05:00 • committed by Sylvestre Ledru
parent 45b29d287f
commit 5e7d58650d
4 changed files with 53 additions and 27 deletions
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7
tests/by-util/test_pinky.rs
View file

@ -24,11 +24,14 @@ fn test_capitalize() {
fn test_long_format() {
let login = "root";
let pw: Passwd = Passwd::locate(login).unwrap();
let real_name = pw.user_info.replace('&', &pw.name.capitalize());
let user_info = pw.user_info.unwrap_or_default();
let user_dir = pw.user_dir.unwrap_or_default();
let user_shell = pw.user_shell.unwrap_or_default();
let real_name = user_info.replace('&', &pw.name.capitalize());
let ts = TestScenario::new(util_name!());
ts.ucmd().arg("-l").arg(login).succeeds().stdout_is(format!(
"Login name: {:<28}In real life: {}\nDirectory: {:<29}Shell: {}\n\n",
login, real_name, pw.user_dir, pw.user_shell
login, real_name, user_dir, user_shell
));
ts.ucmd()