5.4-stable review patch. If anyone has any objections, please let me know.
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From: Claudio Imbrenda imbrenda@linux.ibm.com
[ Upstream commit cff59d8631e1409ffdd22d9d717e15810181b32c ]
The return value uv_set_shared() and uv_remove_shared() (which are wrappers around the share() function) is not always checked. The system integrity of a protected guest depends on the Share and Unshare UVCs being successful. This means that any caller that fails to check the return value will compromise the security of the protected guest.
No code path that would lead to such violation of the security guarantees is currently exercised, since all the areas that are shared never get unshared during the lifetime of the system. This might change and become an issue in the future.
The Share and Unshare UVCs can only fail in case of hypervisor misbehaviour (either a bug or malicious behaviour). In such cases there is no reasonable way forward, and the system needs to panic.
This patch replaces the return at the end of the share() function with a panic, to guarantee system integrity.
Fixes: 5abb9351dfd9 ("s390/uv: introduce guest side ultravisor code") Signed-off-by: Claudio Imbrenda imbrenda@linux.ibm.com Reviewed-by: Christian Borntraeger borntraeger@linux.ibm.com Reviewed-by: Steffen Eiden seiden@linux.ibm.com Reviewed-by: Janosch Frank frankja@linux.ibm.com Link: https://lore.kernel.org/r/20240801112548.85303-1-imbrenda@linux.ibm.com Message-ID: 20240801112548.85303-1-imbrenda@linux.ibm.com [frankja@linux.ibm.com: Fixed up patch subject] Signed-off-by: Janosch Frank frankja@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/include/asm/uv.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h index ef3c00b049ab4..67f63b76dc18b 100644 --- a/arch/s390/include/asm/uv.h +++ b/arch/s390/include/asm/uv.h @@ -97,7 +97,10 @@ static inline int share(unsigned long addr, u16 cmd)
if (!uv_call(0, (u64)&uvcb)) return 0; - return -EINVAL; + pr_err("%s UVC failed (rc: 0x%x, rrc: 0x%x), possible hypervisor bug.\n", + uvcb.header.cmd == UVC_CMD_SET_SHARED_ACCESS ? "Share" : "Unshare", + uvcb.header.rc, uvcb.header.rrc); + panic("System security cannot be guaranteed unless the system panics now.\n"); }
/*