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binder: Check for underflow when subtracting from user-provided value. #375

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Merged
wedsonaf merged 1 commit into from
Jun 11, 2021
Merged

binder: Check for underflow when subtracting from user-provided value. #375

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17 changes: 11 additions & 6 deletions drivers/android/process.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -545,7 +545,7 @@ impl Process {
pub(crate) fn buffer_get(&self, ptr: usize) -> Option<Allocation> {
let mut inner = self.inner.lock();
let mapping = inner.mapping.as_mut()?;
let offset = ptr - mapping.address;
let offset = ptr.checked_sub(mapping.address)?;
let (size, odata) = mapping.alloc.reserve_existing(offset).ok()?;
let mut alloc = Allocation::new(self, offset, size, ptr, mapping.pages.clone());
if let Some(data) = odata {
Expand All @@ -557,12 +557,17 @@ impl Process {
pub(crate) fn buffer_raw_free(&self, ptr: usize) {
let mut inner = self.inner.lock();
if let Some(ref mut mapping) = &mut inner.mapping {
if mapping
.alloc
.reservation_abort(ptr - mapping.address)
.is_err()
if ptr < mapping.address
|| mapping
.alloc
.reservation_abort(ptr - mapping.address)
.is_err()
{
pr_warn!("Offset {} failed to free\n", ptr - mapping.address);
pr_warn!(
"Pointer {:x} failed to free, base = {:x}\n",
ptr,
mapping.address
);
}
}
}
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