PCI: Return ~0 data on pciconfig_read() CAP_SYS_ADMIN failure
stable inclusion from linux-4.19.207 commit 60242386c7ef9b084fc138e3d2b7bb99042fd779 -------------------------------- commit a8bd29bd upstream. The pciconfig_read() syscall reads PCI configuration space using hardware-dependent config accessors. If the read fails on PCI, most accessors don't return an error; they pretend the read was successful and got ~0 data from the device, so the syscall returns success with ~0 data in the buffer. When the accessor does return an error, pciconfig_read() normally fills the user's buffer with ~0 and returns an error in errno. But after e4585da2 ("pci syscall.c: Switch to refcounting API"), we don't fill the buffer with ~0 for the EPERM "user lacks CAP_SYS_ADMIN" error. Userspace may rely on the ~0 data to detect errors, but after e4585da2, that would not detect CAP_SYS_ADMIN errors. Restore the original behaviour of filling the buffer with ~0 when the CAP_SYS_ADMIN check fails. [bhelgaas: commit log, fold in Nathan's fix https://lore.kernel.org/r/20210803200836.500658-1-nathan@kernel.org] Fixes: e4585da2 ("pci syscall.c: Switch to refcounting API") Link: https://lore.kernel.org/r/20210729233755.1509616-1-kw@linux.comSigned-off-by: NKrzysztof Wilczyński <kw@linux.com> Signed-off-by: NBjorn Helgaas <bhelgaas@google.com> Cc: stable@vger.kernel.org Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
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