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Kernel: Add FileDescription read/write API that bypasses current offset

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Forcing users of a FileDescription to seek before they can read/write
makes it inherently racy. This patch adds variants of read/write that
simply ignore the "current offset" of the description in favor of a
caller-supplied offset.
This commit is contained in:
Andreas Kling 2021-07-16 00:35:48 +02:00
parent ace8b9a0ee
commit d1395f2eb9
Notes: sideshowbarker 2024-07-18 08:57:14 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/d1395f2eb94
2 changed files with 18 additions and 0 deletions
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14
Kernel/FileSystem/FileDescription.cpp
View file

@ -157,6 +157,20 @@ KResultOr<off_t> FileDescription::seek(off_t offset, int whence)
return m_current_offset;
}
KResultOr<size_t> FileDescription::read(UserOrKernelBuffer& buffer, u64 offset, size_t count)
{
if (Checked<u64>::addition_would_overflow(offset, count))
return EOVERFLOW;
return m_file->read(*this, offset, buffer, count);
}
KResultOr<size_t> FileDescription::write(u64 offset, UserOrKernelBuffer const& data, size_t data_size)
{
if (Checked<u64>::addition_would_overflow(offset, data_size))
return EOVERFLOW;
return m_file->write(*this, offset, data, data_size);
}
KResultOr<size_t> FileDescription::read(UserOrKernelBuffer& buffer, size_t count)
{
Locker locker(m_lock);

4
Kernel/FileSystem/FileDescription.h
View file

@ -51,6 +51,10 @@ public:
KResultOr<size_t> write(const UserOrKernelBuffer& data, size_t);
KResult stat(::stat&);
// NOTE: These ignore the current offset of this file description.
KResultOr<size_t> read(UserOrKernelBuffer&, u64 offset, size_t);
KResultOr<size_t> write(u64 offset, UserOrKernelBuffer const&, size_t);
KResult chmod(mode_t);
bool can_read() const;