[PATCH v1 proxmox 1/6] uuid: avoid potential null dereference and memory leaks

[Robert Obkircher <r.obkircher@proxmox.com>]

Avoid null pointer dereferences on allocation failures and do not leak
memory on the error paths.

I'm also not fully convinced that writing to uninitialized memory via
assingment instead of ptr::write was guaranteed to be safe, but Miri
doesn't complain about it. See the link for some additional context.

Link: https://github.com/rust-lang/unsafe-code-guidelines/issues/346
Signed-off-by: Robert Obkircher <r.obkircher@proxmox.com>
---
 proxmox-uuid/src/lib.rs | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/proxmox-uuid/src/lib.rs b/proxmox-uuid/src/lib.rs
index f2658ec6..59750a3a 100644
--- a/proxmox-uuid/src/lib.rs
+++ b/proxmox-uuid/src/lib.rs
@@ -61,10 +61,9 @@ pub struct Uuid(Box<[u8; 16]>);
 impl Uuid {
     /// Generate a uuid with `uuid_generate(3)`.
     pub fn generate() -> Self {
-        use std::alloc::{Layout, alloc};
-        let uuid = unsafe { alloc(Layout::new::<[u8; 16]>()) as *mut [u8; 16] };
-        unsafe { uuid_generate(uuid) };
-        Self(unsafe { Box::from_raw(uuid) })
+        let mut uuid = Box::new_uninit();
+        unsafe { uuid_generate(uuid.as_mut_ptr()) };
+        Self(unsafe { uuid.assume_init() })
     }
 
     /// Get a reference to the internal 16 byte array.
@@ -92,12 +91,10 @@ impl Uuid {
     /// assert_eq!(uuid1, uuid2);
     /// ```
     pub fn parse_str(src: &str) -> Result<Self, UuidError> {
-        use std::alloc::{Layout, alloc};
-        let uuid: *mut [u8; 16] = unsafe { alloc(Layout::new::<[u8; 16]>()) as *mut [u8; 16] };
+        let mut uuid = [0; 16];
         if src.len() == 36 {
             // Unfortunately the manpage of `uuid_parse(3)` states that it technically requires a
             // terminating null byte at the end, which we don't have, so do this manually:
-            let uuid: &mut [u8] = unsafe { &mut (&mut *uuid)[..] };
             let src = src.as_bytes();
             if src[8] != b'-' || src[13] != b'-' || src[18] != b'-' || src[23] != b'-' {
                 return Err(UuidError);
@@ -118,7 +115,6 @@ impl Uuid {
                 uuid[i] = (hex_digit(src[2 * i + 4])? << 4) | hex_digit(src[2 * i + 5])?;
             }
         } else if src.len() == 32 {
-            let uuid: &mut [u8] = unsafe { &mut (&mut *uuid)[..] };
             let src = src.as_bytes();
             for i in 0..16 {
                 uuid[i] = (hex_digit(src[2 * i])? << 4) | hex_digit(src[2 * i + 1])?;
@@ -126,7 +122,7 @@ impl Uuid {
         } else {
             return Err(UuidError);
         }
-        Ok(Self(unsafe { Box::from_raw(uuid) }))
+        Ok(Self(Box::new(uuid)))
     }
 }
 
-- 
2.47.3