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Prevent reading over a page boundary in mem.indexOfSentinel

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The size of the slice element was not correctly taken into account when determining whether a read would cross a page boundary.
This commit is contained in:
Carl Åstholm 2023-12-19 21:14:48 +01:00
parent 4129996211
commit 781c3a985c
1 changed files with 3 additions and 2 deletions
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5
lib/std/mem.zig
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@ -967,14 +967,15 @@ pub fn indexOfSentinel(comptime T: type, comptime sentinel: T, p: [*:sentinel]co
// as we don't read into a new page. This should be the case for most architectures
// which use paged memory, however should be confirmed before adding a new arch below.
.aarch64, .x86, .x86_64 => if (std.simd.suggestVectorSize(T)) |block_len| {
comptime std.debug.assert(std.mem.page_size % block_len == 0);
const Block = @Vector(block_len, T);
const mask: Block = @splat(sentinel);
comptime std.debug.assert(std.mem.page_size % @sizeOf(Block) == 0);
// First block may be unaligned
const start_addr = @intFromPtr(&p[i]);
const offset_in_page = start_addr & (std.mem.page_size - 1);
if (offset_in_page < std.mem.page_size - block_len) {
if (offset_in_page < std.mem.page_size - @sizeOf(Block)) {
// Will not read past the end of a page, full block.
const block: Block = p[i..][0..block_len].*;
const matches = block == mask;