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Ext2FS: Zero out new space when growing an inode

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Before this change, truncating an Ext2FS inode to a larger size than it
was before would give you uninitialized on-disk data.

Fix this by zeroing out all the new space when doing an inode resize.

This is pretty naively implemented via Inode::write_bytes() and there's
lots of room for cleverness here in the future.
This commit is contained in:
Andreas Kling 2021-01-09 22:05:05 +01:00
parent f0093e5d59
commit 77656aed8e
1 changed files with 18 additions and 0 deletions
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18
Kernel/FileSystem/Ext2FileSystem.cpp
View file

@ -804,6 +804,24 @@ KResult Ext2FSInode::resize(u64 new_size)
set_metadata_dirty(true);
m_block_list = move(block_list);
if (new_size > old_size) {
// If we're growing the inode, make sure we zero out all the new space.
// FIXME: There are definitely more efficient ways to achieve this.
size_t bytes_to_clear = new_size - old_size;
size_t clear_from = old_size;
u8 zero_buffer[PAGE_SIZE];
memset(zero_buffer, 0, sizeof(zero_buffer));
while (bytes_to_clear) {
auto nwritten = write_bytes(clear_from, min(sizeof(zero_buffer), bytes_to_clear), UserOrKernelBuffer::for_kernel_buffer(zero_buffer), nullptr);
if (nwritten < 0)
return KResult(-nwritten);
ASSERT(nwritten != 0);
bytes_to_clear -= nwritten;
clear_from += nwritten;
}
}
return KSuccess;
}