| Message ID | 20240819123508.217444-1-frediano.ziglio@cloud.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] Avoid crash calling PrintErrMesg from efi_multiboot2 | expand |
On 19.08.2024 14:35, Frediano Ziglio wrote: > Although code is compiled with -fpic option data is not position > independent. This causes data pointer to become invalid if > code is not relocated properly which is what happens for > efi_multiboot2 which is called by multiboot entry code. > > Code tested adding > PrintErrMesg(L"Test message", EFI_BUFFER_TOO_SMALL); > in efi_multiboot2 before calling efi_arch_edd (this function > can potentially call PrintErrMesg). > > Before the patch (XenServer installation on Qemu, xen replaced > with vanilla xen.gz): > Booting `XenServer (Serial)'Booting `XenServer (Serial)' > Test message: !!!! X64 Exception Type - 0E(#PF - Page-Fault) CPU Apic ID - 00000000 !!!! > ExceptionData - 0000000000000000 I:0 R:0 U:0 W:0 P:0 PK:0 SS:0 SGX:0 > RIP - 000000007DC29E46, CS - 0000000000000038, RFLAGS - 0000000000210246 > RAX - 0000000000000000, RCX - 0000000000000050, RDX - 0000000000000000 > RBX - 000000007DAB4558, RSP - 000000007EFA1200, RBP - 0000000000000000 > RSI - FFFF82D040467A88, RDI - 0000000000000000 > R8 - 000000007EFA1238, R9 - 000000007EFA1230, R10 - 0000000000000000 > R11 - 000000007CF42665, R12 - FFFF82D040467A88, R13 - 000000007EFA1228 > R14 - 000000007EFA1225, R15 - 000000007DAB45A8 > DS - 0000000000000030, ES - 0000000000000030, FS - 0000000000000030 > GS - 0000000000000030, SS - 0000000000000030 > CR0 - 0000000080010033, CR2 - FFFF82D040467A88, CR3 - 000000007EC01000 > CR4 - 0000000000000668, CR8 - 0000000000000000 > DR0 - 0000000000000000, DR1 - 0000000000000000, DR2 - 0000000000000000 > DR3 - 0000000000000000, DR6 - 00000000FFFF0FF0, DR7 - 0000000000000400 > GDTR - 000000007E9E2000 0000000000000047, LDTR - 0000000000000000 > IDTR - 000000007E4E5018 0000000000000FFF, TR - 0000000000000000 > FXSAVE_STATE - 000000007EFA0E60 > !!!! Find image based on IP(0x7DC29E46) (No PDB) (ImageBase=000000007DC28000, EntryPoint=000000007DC2B917) !!!! > > After the patch: > Booting `XenServer (Serial)'Booting `XenServer (Serial)' > Test message: Buffer too small > BdsDxe: loading Boot0000 "UiApp" from Fv(7CB8BDC9-F8EB-4F34-AAEA-3EE4AF6516A1)/FvFile(462CAA21-7614-4503-836E-8AB6F4662331) > BdsDxe: starting Boot0000 "UiApp" from Fv(7CB8BDC9-F8EB-4F34-AAEA-3EE4AF6516A1)/FvFile(462CAA21-7614-4503-836E-8AB6F4662331) > > Fixes: 00d5d5ce23e6 ("work around Clang generating .data.rel.ro section for init-only files") I don't think this is right. While this is where the array was introduced, it was correct at that time afaict. It went wrong when MB2 support was added about a year later. 9180f5365524 ("x86: add multiboot2 protocol support for EFI platforms") may be reasonable to blame, albeit I'm not sure that was the final one, after which MB2 support was considered complete. > @@ -308,7 +325,7 @@ static void __init PrintErrMesg(const CHAR16 *mesg, EFI_STATUS ErrCode) > PrintErr(L": "); > > if( (ErrIdx < ARRAY_SIZE(ErrCodeToStr)) && ErrCodeToStr[ErrIdx] ) > - mesg = ErrCodeToStr[ErrIdx]; > + mesg = (const CHAR16 *)((const void *)&ErrorStrings + ErrCodeToStr[ErrIdx]); As said when suggesting the alternative form in reply to v1: This is now too long and hence needs wrapping. Jan
diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c index efbec00af9..bbcd9263e1 100644 --- a/xen/common/efi/boot.c +++ b/xen/common/efi/boot.c @@ -287,19 +287,36 @@ static bool __init match_guid(const EFI_GUID *guid1, const EFI_GUID *guid2) /* generic routine for printing error messages */ static void __init PrintErrMesg(const CHAR16 *mesg, EFI_STATUS ErrCode) { - static const CHAR16* const ErrCodeToStr[] __initconstrel = { - [~EFI_ERROR_MASK & EFI_NOT_FOUND] = L"Not found", - [~EFI_ERROR_MASK & EFI_NO_MEDIA] = L"The device has no media", - [~EFI_ERROR_MASK & EFI_MEDIA_CHANGED] = L"Media changed", - [~EFI_ERROR_MASK & EFI_DEVICE_ERROR] = L"Device error", - [~EFI_ERROR_MASK & EFI_VOLUME_CORRUPTED] = L"Volume corrupted", - [~EFI_ERROR_MASK & EFI_ACCESS_DENIED] = L"Access denied", - [~EFI_ERROR_MASK & EFI_OUT_OF_RESOURCES] = L"Out of resources", - [~EFI_ERROR_MASK & EFI_VOLUME_FULL] = L"Volume is full", - [~EFI_ERROR_MASK & EFI_SECURITY_VIOLATION] = L"Security violation", - [~EFI_ERROR_MASK & EFI_CRC_ERROR] = L"CRC error", - [~EFI_ERROR_MASK & EFI_COMPROMISED_DATA] = L"Compromised data", - [~EFI_ERROR_MASK & EFI_BUFFER_TOO_SMALL] = L"Buffer too small", +#define ERROR_MESSAGE_LIST \ + ERROR_MESSAGE(EFI_NOT_FOUND, "Not found") \ + ERROR_MESSAGE(EFI_NO_MEDIA, "The device has no media") \ + ERROR_MESSAGE(EFI_MEDIA_CHANGED, "Media changed") \ + ERROR_MESSAGE(EFI_DEVICE_ERROR, "Device error") \ + ERROR_MESSAGE(EFI_VOLUME_CORRUPTED, "Volume corrupted") \ + ERROR_MESSAGE(EFI_ACCESS_DENIED, "Access denied") \ + ERROR_MESSAGE(EFI_OUT_OF_RESOURCES, "Out of resources") \ + ERROR_MESSAGE(EFI_VOLUME_FULL, "Volume is full") \ + ERROR_MESSAGE(EFI_SECURITY_VIOLATION, "Security violation") \ + ERROR_MESSAGE(EFI_CRC_ERROR, "CRC error") \ + ERROR_MESSAGE(EFI_COMPROMISED_DATA, "Compromised data") \ + ERROR_MESSAGE(EFI_BUFFER_TOO_SMALL, "Buffer too small") + + static const struct ErrorStrings { + CHAR16 start; +#undef ERROR_MESSAGE +#define ERROR_MESSAGE(code, str) CHAR16 msg_ ## code[sizeof(str)]; + ERROR_MESSAGE_LIST + } ErrorStrings __initconst = { + 0 +#undef ERROR_MESSAGE +#define ERROR_MESSAGE(code, str) , L ## str + ERROR_MESSAGE_LIST + }; + static const uint16_t ErrCodeToStr[] __initconst = { +#undef ERROR_MESSAGE +#define ERROR_MESSAGE(code, str) \ + [~EFI_ERROR_MASK & code] = offsetof(struct ErrorStrings, msg_ ## code), + ERROR_MESSAGE_LIST }; EFI_STATUS ErrIdx = ErrCode & ~EFI_ERROR_MASK; @@ -308,7 +325,7 @@ static void __init PrintErrMesg(const CHAR16 *mesg, EFI_STATUS ErrCode) PrintErr(L": "); if( (ErrIdx < ARRAY_SIZE(ErrCodeToStr)) && ErrCodeToStr[ErrIdx] ) - mesg = ErrCodeToStr[ErrIdx]; + mesg = (const CHAR16 *)((const void *)&ErrorStrings + ErrCodeToStr[ErrIdx]); else { PrintErr(L"ErrCode: ");
Although code is compiled with -fpic option data is not position independent. This causes data pointer to become invalid if code is not relocated properly which is what happens for efi_multiboot2 which is called by multiboot entry code. Code tested adding PrintErrMesg(L"Test message", EFI_BUFFER_TOO_SMALL); in efi_multiboot2 before calling efi_arch_edd (this function can potentially call PrintErrMesg). Before the patch (XenServer installation on Qemu, xen replaced with vanilla xen.gz): Booting `XenServer (Serial)'Booting `XenServer (Serial)' Test message: !!!! X64 Exception Type - 0E(#PF - Page-Fault) CPU Apic ID - 00000000 !!!! ExceptionData - 0000000000000000 I:0 R:0 U:0 W:0 P:0 PK:0 SS:0 SGX:0 RIP - 000000007DC29E46, CS - 0000000000000038, RFLAGS - 0000000000210246 RAX - 0000000000000000, RCX - 0000000000000050, RDX - 0000000000000000 RBX - 000000007DAB4558, RSP - 000000007EFA1200, RBP - 0000000000000000 RSI - FFFF82D040467A88, RDI - 0000000000000000 R8 - 000000007EFA1238, R9 - 000000007EFA1230, R10 - 0000000000000000 R11 - 000000007CF42665, R12 - FFFF82D040467A88, R13 - 000000007EFA1228 R14 - 000000007EFA1225, R15 - 000000007DAB45A8 DS - 0000000000000030, ES - 0000000000000030, FS - 0000000000000030 GS - 0000000000000030, SS - 0000000000000030 CR0 - 0000000080010033, CR2 - FFFF82D040467A88, CR3 - 000000007EC01000 CR4 - 0000000000000668, CR8 - 0000000000000000 DR0 - 0000000000000000, DR1 - 0000000000000000, DR2 - 0000000000000000 DR3 - 0000000000000000, DR6 - 00000000FFFF0FF0, DR7 - 0000000000000400 GDTR - 000000007E9E2000 0000000000000047, LDTR - 0000000000000000 IDTR - 000000007E4E5018 0000000000000FFF, TR - 0000000000000000 FXSAVE_STATE - 000000007EFA0E60 !!!! Find image based on IP(0x7DC29E46) (No PDB) (ImageBase=000000007DC28000, EntryPoint=000000007DC2B917) !!!! After the patch: Booting `XenServer (Serial)'Booting `XenServer (Serial)' Test message: Buffer too small BdsDxe: loading Boot0000 "UiApp" from Fv(7CB8BDC9-F8EB-4F34-AAEA-3EE4AF6516A1)/FvFile(462CAA21-7614-4503-836E-8AB6F4662331) BdsDxe: starting Boot0000 "UiApp" from Fv(7CB8BDC9-F8EB-4F34-AAEA-3EE4AF6516A1)/FvFile(462CAA21-7614-4503-836E-8AB6F4662331) Fixes: 00d5d5ce23e6 ("work around Clang generating .data.rel.ro section for init-only files") Signed-off-by: Frediano Ziglio <frediano.ziglio@cloud.com> --- xen/common/efi/boot.c | 45 +++++++++++++++++++++++++++++-------------- 1 file changed, 31 insertions(+), 14 deletions(-) --- Changes since v1: - added "Fixes:" tag; - fixed cast style change.