Maybe unsound in set_argv_index and set_omit

[lwz23]

hello, thank you for your contribution in this project, I am scanning the unsoundness problem in rust project.
I notice the following code:

pub fn set_argv_index(&mut self, i: i32) {
        unsafe { (*self.usage).argvIndex = i };
    }
    pub fn set_omit(&mut self, value: bool) {
        unsafe { (*self.usage).omit = u8::from(value) }
    }

Considering that pub mod table and usage is a pub field, I assume that users can directly manipulate this field, and that set_argv_index is a public function. This potential situation could result in self.usage being a null pointer, and directly dereferencing it might trigger undefined behavior (UB). For safety reasons, I felt it necessary to report this issue. If you have performed checks elsewhere that ensure this is safe, please don’t take offense at my raising this issue.

[lwz23]

here is my PoC:

use std::ptr;

pub struct sqlite3_index_info_sqlite3_index_constraint_usage {
    pub argvIndex: i32,
    pub omit: u8,
}

pub struct Constraint {
    //pub constraint: sqlite3_index_info_sqlite3_index_constraint,
    pub usage: *mut sqlite3_index_info_sqlite3_index_constraint_usage,
    // needed for sqlite3_vtab_* methods
    //index_info: *mut sqlite3_index_info,
    constraint_idx: i32,
}

impl Constraint {
    pub fn set_argv_index(&mut self, i: i32) {
        unsafe { (*self.usage).argvIndex = i };
    }
    pub fn set_omit(&mut self, value: bool) {
        unsafe { (*self.usage).omit = u8::from(value) }
    }
}

fn main(){
    let a:*mut sqlite3_index_info_sqlite3_index_constraint_usage= ptr::null_mut();
    let mut b=Constraint{usage: a, constraint_idx: 0};
    b.set_argv_index(1);
}

I annotated and modified parts of the implementation for convenience, but I believe the overall framework is consistent.

[lwz23]

Maybe same unsoundness problem for

sqlite-loadable-rs/src/table.rs

Line 253 in 2c5c049

pub fn new(list_value: *mut sqlite3_value) -> Self {

but this is because the new method didn't varify the pointer validity.
and if pass a null pointer it may cause UB in

sqlite-loadable-rs/src/table.rs

Line 268 in 2c5c049

unsafe { sqlite3ext_vtab_in_first(self.list_value, &mut self.value) }