uaccess: Prepare for masked user access on powerpc #382
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Following patch will add missing barrier_nospec() to copy_from_user_iter(). On some architecture like x86 it might degrade performance, which would be unfortunate as copy_from_user_iter() is a critical function. Convert copy_from_user_iter() to using masked user access on architecture that support it. This is similar to what was done for copy_from_user() by commit 0fc810a ("x86/uaccess: Avoid barrier_nospec() in 64-bit copy_from_user()") Signed-off-by: Christophe Leroy <[email protected]>
The results of "access_ok()" can be mis-speculated. The result is that you can end speculatively: if (access_ok(from, size)) // Right here For the same reason as done in copy_from_user() by commit 74e19ef ("uaccess: Add speculation barrier to copy_from_user()"), add a speculation barrier to copy_from_user_iter(). Signed-off-by: Christophe Leroy <[email protected]>
Replace the open coded implementation with the scoped user access guards. No functional change intended. Signed-off-by: Christophe Leroy <[email protected]>
…uired Properly use masked_user_read_access_begin() and masked_user_write_access_begin() instead of masked_user_access_begin() in order to match user_read_access_end() and user_write_access_end(). This is important for architectures like powerpc that enable separately user reads and user writes. That means masked_user_read_access_begin() is used when user memory is exclusively read during the window and masked_user_write_access_begin() is used when user memory is exclusively writen during the window. masked_user_access_begin() remains and is used when both reads and writes are performed during the open window. Each of them is expected to be terminated by the matching user_read_access_end(), user_write_access_end() and user_access_end(). Signed-off-by: Christophe Leroy <[email protected]>
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Pull request for series with
subject: uaccess: Prepare for masked user access on powerpc
version: 5
url: https://patchwork.kernel.org/project/linux-block/list/?series=1024396