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Kernel: Make copy_to/from_user safe and remove unnecessary checks

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Since the CPU already does almost all necessary validation steps
for us, we don't really need to attempt to do this. Doing it
ourselves doesn't really work very reliably, because we'd have to
account for other processors modifying virtual memory, and we'd
have to account for e.g. pages not being able to be allocated
due to insufficient resources.

So change the copy_to/from_user (and associated helper functions)
to use the new safe_memcpy, which will return whether it succeeded
or not. The only manual validation step needed (which the CPU
can't perform for us) is making sure the pointers provided by user
mode aren't pointing to kernel mappings.

To make it easier to read/write from/to either kernel or user mode
data add the UserOrKernelBuffer helper class, which will internally
either use copy_from/to_user or directly memcpy, or pass the data
through directly using a temporary buffer on the stack.

Last but not least we need to keep syscall params trivial as we
need to copy them from/to user mode using copy_from/to_user.
This commit is contained in:
Tom 2020-09-11 21:11:07 -06:00 • committed by Andreas Kling
parent 7d1b8417bd
commit c8d9f1b9c9
149 changed files with 1585 additions and 1244 deletions
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49
Kernel/Devices/PATAChannel.cpp
View file

@ -274,11 +274,11 @@ void PATAChannel::detect_disks()
}
}
bool PATAChannel::ata_read_sectors_with_dma(u32 lba, u16 count, u8* outbuf, bool slave_request)
bool PATAChannel::ata_read_sectors_with_dma(u32 lba, u16 count, UserOrKernelBuffer& outbuf, bool slave_request)
{
LOCKER(s_lock());
#ifdef PATA_DEBUG
dbg() << "PATAChannel::ata_read_sectors_with_dma (" << lba << " x" << count << ") -> " << outbuf;
dbg() << "PATAChannel::ata_read_sectors_with_dma (" << lba << " x" << count << ") -> " << outbuf.user_or_kernel_ptr();
#endif
prdt().offset = m_dma_buffer_page->paddr();
@ -335,24 +335,26 @@ bool PATAChannel::ata_read_sectors_with_dma(u32 lba, u16 count, u8* outbuf, bool
if (m_device_error)
return false;
memcpy(outbuf, m_dma_buffer_page->paddr().offset(0xc0000000).as_ptr(), 512 * count);
if (!outbuf.write(m_dma_buffer_page->paddr().offset(0xc0000000).as_ptr(), 512 * count))
return false; // TODO: -EFAULT
// I read somewhere that this may trigger a cache flush so let's do it.
m_bus_master_base.offset(2).out<u8>(m_bus_master_base.offset(2).in<u8>() | 0x6);
return true;
}
bool PATAChannel::ata_write_sectors_with_dma(u32 lba, u16 count, const u8* inbuf, bool slave_request)
bool PATAChannel::ata_write_sectors_with_dma(u32 lba, u16 count, const UserOrKernelBuffer& inbuf, bool slave_request)
{
LOCKER(s_lock());
#ifdef PATA_DEBUG
dbg() << "PATAChannel::ata_write_sectors_with_dma (" << lba << " x" << count << ") <- " << inbuf;
dbg() << "PATAChannel::ata_write_sectors_with_dma (" << lba << " x" << count << ") <- " << inbuf.user_or_kernel_ptr();
#endif
prdt().offset = m_dma_buffer_page->paddr();
prdt().size = 512 * count;
memcpy(m_dma_buffer_page->paddr().offset(0xc0000000).as_ptr(), inbuf, 512 * count);
if (!inbuf.read(m_dma_buffer_page->paddr().offset(0xc0000000).as_ptr(), 512 * count))
return false; // TODO: -EFAULT
ASSERT(prdt().size <= PAGE_SIZE);
@ -406,12 +408,12 @@ bool PATAChannel::ata_write_sectors_with_dma(u32 lba, u16 count, const u8* inbuf
return true;
}
bool PATAChannel::ata_read_sectors(u32 lba, u16 count, u8* outbuf, bool slave_request)
bool PATAChannel::ata_read_sectors(u32 lba, u16 count, UserOrKernelBuffer& outbuf, bool slave_request)
{
ASSERT(count <= 256);
LOCKER(s_lock());
#ifdef PATA_DEBUG
dbg() << "PATAChannel::ata_read_sectors request (" << count << " sector(s) @ " << lba << " into " << outbuf << ")";
dbg() << "PATAChannel::ata_read_sectors request (" << count << " sector(s) @ " << lba << " into " << outbuf.user_or_kernel_ptr() << ")";
#endif
while (m_io_base.offset(ATA_REG_STATUS).in<u8>() & ATA_SR_BSY)
@ -460,14 +462,21 @@ bool PATAChannel::ata_read_sectors(u32 lba, u16 count, u8* outbuf, bool slave_re
u8 status = m_control_base.offset(ATA_CTL_ALTSTATUS).in<u8>();
ASSERT(!(status & ATA_SR_BSY));
auto* buffer = (u16*)(outbuf + i * 512);
auto out = outbuf.offset(i * 512);
#ifdef PATA_DEBUG
dbg() << "PATAChannel: Retrieving 512 bytes (part " << i << ") (status=" << String::format("%b", status) << "), outbuf=(" << buffer << ")...";
dbg() << "PATAChannel: Retrieving 512 bytes (part " << i << ") (status=" << String::format("%b", status) << "), outbuf=(" << out.user_or_kernel_ptr() << ")...";
#endif
prepare_for_irq();
for (int i = 0; i < 256; i++) {
buffer[i] = IO::in16(m_io_base.offset(ATA_REG_DATA).get());
ssize_t nwritten = out.write_buffered<512>(512, [&](u8* buffer, size_t buffer_bytes) {
for (size_t i = 0; i < buffer_bytes; i += sizeof(u16))
*(u16*)&buffer[i] = IO::in16(m_io_base.offset(ATA_REG_DATA).get());
return (ssize_t)buffer_bytes;
});
if (nwritten < 0) {
sti();
disable_irq();
return false; // TODO: -EFAULT
}
}
@ -476,7 +485,7 @@ bool PATAChannel::ata_read_sectors(u32 lba, u16 count, u8* outbuf, bool slave_re
return true;
}
bool PATAChannel::ata_write_sectors(u32 start_sector, u16 count, const u8* inbuf, bool slave_request)
bool PATAChannel::ata_write_sectors(u32 start_sector, u16 count, const UserOrKernelBuffer& inbuf, bool slave_request)
{
ASSERT(count <= 256);
LOCKER(s_lock());
@ -515,17 +524,21 @@ bool PATAChannel::ata_write_sectors(u32 start_sector, u16 count, const u8* inbuf
u8 status = m_io_base.offset(ATA_REG_STATUS).in<u8>();
ASSERT(status & ATA_SR_DRQ);
auto in = inbuf.offset(i * 512);
#ifdef PATA_DEBUG
dbg() << "PATAChannel: Writing 512 bytes (part " << i << ") (status=" << String::format("%b", status) << "), inbuf=(" << (inbuf + (512 * i)) << ")...";
dbg() << "PATAChannel: Writing 512 bytes (part " << i << ") (status=" << String::format("%b", status) << "), inbuf=(" << in.user_or_kernel_ptr() << ")...";
#endif
prepare_for_irq();
auto* buffer = (u16*)(const_cast<u8*>(inbuf) + i * 512);
for (int i = 0; i < 256; i++) {
IO::out16(m_io_base.offset(ATA_REG_DATA).get(), buffer[i]);
}
ssize_t nread = in.read_buffered<512>(512, [&](const u8* buffer, size_t buffer_bytes) {
for (size_t i = 0; i < buffer_bytes; i += sizeof(u16))
IO::out16(m_io_base.offset(ATA_REG_DATA).get(), *(const u16*)&buffer[i]);
return (ssize_t)buffer_bytes;
});
wait_for_irq();
status = m_io_base.offset(ATA_REG_STATUS).in<u8>();
ASSERT(!(status & ATA_SR_BSY));
if (nread < 0)
return false; // TODO: -EFAULT
}
prepare_for_irq();
m_io_base.offset(ATA_REG_COMMAND).out<u8>(ATA_CMD_CACHE_FLUSH);