path: root/scripts
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authorDave Martin <Dave.Martin@arm.com>2018-03-28 10:50:49 +0100
committerWill Deacon <will.deacon@arm.com>2018-03-28 15:25:44 +0100
commit65896545b69ffaac947c12e11d3dcc57fd1fb772 (patch)
treec867c9e469ac9e2003877985e5dd04d97e2aa222 /scripts
parent20b8547277a6e8ee1d928792c1b2782c9a2a6cf5 (diff)
arm64: uaccess: Fix omissions from usercopy whitelist
When the hardend usercopy support was added for arm64, it was concluded that all cases of usercopy into and out of thread_struct were statically sized and so didn't require explicit whitelisting of the appropriate fields in thread_struct. Testing with usercopy hardening enabled has revealed that this is not the case for certain ptrace regset manipulation calls on arm64. This occurs because the sizes of usercopies associated with the regset API are dynamic by construction, and because arm64 does not always stage such copies via the stack: indeed the regset API is designed to avoid the need for that by adding some bounds checking. This is currently believed to affect only the fpsimd and TLS registers. Because the whitelisted fields in thread_struct must be contiguous, this patch groups them together in a nested struct. It is also necessary to be able to determine the location and size of that struct, so rather than making the struct anonymous (which would save on edits elsewhere) or adding an anonymous union containing named and unnamed instances of the same struct (gross), this patch gives the struct a name and makes the necessary edits to code that references it (noisy but simple). Care is needed to ensure that the new struct does not contain padding (which the usercopy hardening would fail to protect). For this reason, the presence of tp2_value is made unconditional, since a padding field would be needed there in any case. This pads up to the 16-byte alignment required by struct user_fpsimd_state. Acked-by: Kees Cook <keescook@chromium.org> Reported-by: Mark Rutland <mark.rutland@arm.com> Fixes: 9e8084d3f761 ("arm64: Implement thread_struct whitelist for hardened usercopy") Signed-off-by: Dave Martin <Dave.Martin@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
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