From e6b8f35a698e3206c0945a19be4090edfc584c6d Mon Sep 17 00:00:00 2001 From: Robbie Harwood Date: Mon, 10 Apr 2023 16:44:09 +0000 Subject: [PATCH] Fix aa64 page fault with EFI_MEMORY_ATTRIBUTE_PROTOCOL Signed-off-by: Robbie Harwood --- ...b_dl_set_mem_attrs-fix-format-string.patch | 38 +++++ ...attrs-add-self-check-for-the-tramp-G.patch | 140 ++++++++++++++++++ ...ments-page-align-the-tramp-GOT-areas.patch | 70 +++++++++ grub.patches | 3 + grub2.spec | 5 +- 5 files changed, 255 insertions(+), 1 deletion(-) create mode 100644 0329-grub_dl_set_mem_attrs-fix-format-string.patch create mode 100644 0330-grub_dl_set_mem_attrs-add-self-check-for-the-tramp-G.patch create mode 100644 0331-grub_dl_load_segments-page-align-the-tramp-GOT-areas.patch diff --git a/0329-grub_dl_set_mem_attrs-fix-format-string.patch b/0329-grub_dl_set_mem_attrs-fix-format-string.patch new file mode 100644 index 0000000..ee50591 --- /dev/null +++ b/0329-grub_dl_set_mem_attrs-fix-format-string.patch @@ -0,0 +1,38 @@ +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 +From: Laszlo Ersek +Date: Fri, 7 Apr 2023 14:54:35 +0200 +Subject: [PATCH] grub_dl_set_mem_attrs(): fix format string + +The grub_dprintf() call for printing the message + + updating attributes for GOT and trampolines + +passes the argument "mod->name", but the format string doesn't accept that +argument. + +Print the module name too. + +Example output: + +> kern/dl.c:736: updating attributes for GOT and trampolines ("video_fb") + +Fixes: ad1b904d325b (nx: set page permissions for loaded modules.) +Signed-off-by: Laszlo Ersek +--- + grub-core/kern/dl.c | 3 ++- + 1 file changed, 2 insertions(+), 1 deletion(-) + +diff --git a/grub-core/kern/dl.c b/grub-core/kern/dl.c +index ab9101a5ad..a97f4a8b13 100644 +--- a/grub-core/kern/dl.c ++++ b/grub-core/kern/dl.c +@@ -733,7 +733,8 @@ grub_dl_set_mem_attrs (grub_dl_t mod, void *ehdr) + { + tgsz = ALIGN_UP(tgsz, arch_addralign); + +- grub_dprintf ("modules", "updating attributes for GOT and trampolines\n", ++ grub_dprintf ("modules", ++ "updating attributes for GOT and trampolines (\"%s\")\n", + mod->name); + grub_update_mem_attrs (tgaddr, tgsz, GRUB_MEM_ATTR_R|GRUB_MEM_ATTR_X, + GRUB_MEM_ATTR_W); diff --git a/0330-grub_dl_set_mem_attrs-add-self-check-for-the-tramp-G.patch b/0330-grub_dl_set_mem_attrs-add-self-check-for-the-tramp-G.patch new file mode 100644 index 0000000..b95e678 --- /dev/null +++ b/0330-grub_dl_set_mem_attrs-add-self-check-for-the-tramp-G.patch @@ -0,0 +1,140 @@ +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 +From: Laszlo Ersek +Date: Fri, 7 Apr 2023 16:21:54 +0200 +Subject: [PATCH] grub_dl_set_mem_attrs(): add self-check for the tramp/GOT + sizes + +On aarch64 UEFI, we currently have a crasher: + + grub_dl_load_core() + grub_dl_load_core_noinit() + + /* independent allocation: must remain writable */ + mod = grub_zalloc(); + + /* allocates module image with incorrect tail alignment */ + grub_dl_load_segments() + + /* write-protecting the module image makes "mod" read-only! */ + grub_dl_set_mem_attrs() + grub_update_mem_attrs() + + grub_dl_init() + /* page fault, crash */ + mod->next = ...; + +- Commit 887f1d8fa976 ("modules: load module sections at page-aligned + addresses", 2023-02-08) forgot to page-align the allocation of the + trampolines and GOT areas of grub2 modules, in grub_dl_load_segments(). + +- Commit ad1b904d325b ("nx: set page permissions for loaded modules.", + 2023-02-08) calculated a common bounding box for the trampolines and GOT + areas in grub_dl_set_mem_attrs(), rounded the box size up to a whole + multiple of EFI page size ("arch_addralign"), and write-protected the + resultant page range. + +Consequently, grub_dl_load_segments() places the module image in memory +such that its tail -- the end of the trampolines and GOT areas -- lands at +the head of a page whose tail in turn contains independent memory +allocations, such as "mod". grub_dl_set_mem_attrs() will then unwittingly +write-protect these other allocations too. + +But "mod" must remain writable: we assign "mod->next" in grub_dl_init() +subsequently. Currently we crash there with a page fault / permission +fault. + +(The crash is not trivial to hit: the tramp/GOT areas are irrelevant on +x86_64, plus the page protection depends on the UEFI platform firmware +providing EFI_MEMORY_ATTRIBUTE_PROTOCOL. In practice, the crash is +restricted to aarch64 edk2 (ArmVirtQemu) builds containing commit +1c4dfadb4611, "ArmPkg/CpuDxe: Implement EFI memory attributes protocol", +2023-03-16.) + +Example log before the patch: + +> kern/dl.c:736: updating attributes for GOT and trampolines ("video_fb") +> kern/efi/mm.c:927: set +rx -w on 0x13b88b000-0x13b88bfff before:rwx after:r-x +> kern/dl.c:744: done updating module memory attributes for "video_fb" +> kern/dl.c:639: flushing 0xe4f0 bytes at 0x13b87d000 +> kern/arm64/cache.c:42: D$ line size: 64 +> kern/arm64/cache.c:43: I$ line size: 64 +> kern/dl.c:839: module name: video_fb +> kern/dl.c:840: init function: 0x0 +> kern/dl.c:865: Initing module video_fb +> +> Synchronous Exception at 0x000000013B8A76EC +> PC 0x00013B8A76EC +> +> X0 0x000000013B88B960 X1 0x0000000000000000 X2 0x000000013F93587C X3 0x0000000000000075 +> +> SP 0x00000000470745C0 ELR 0x000000013B8A76EC SPSR 0x60000205 FPSR 0x00000000 +> ESR 0x9600004F FAR 0x000000013B88B9D0 +> +> ESR : EC 0x25 IL 0x1 ISS 0x0000004F +> +> Data abort: Permission fault, third level + +Note the following: + +- The whole 4K page at 0x1_3B88_B000 is write-protected. + +- The "video_fb" module actually lives at [0x1_3B87_D000, 0x1_3B88_B4F0) + -- left-inclusive, right-exclusive --; that is, in the last page (at + 0x1_3B88_B000), it only occupies the first 0x4F0 bytes. + +- The instruction at 0x1_3B8A_76EC faults. Not shown here, but it is a + store instruction, which writes to the field at offset 0x70 of the + structure pointed-to by the X0 register. This is the "mod->next" + assignment from grub_dl_init(). + +- The faulting address is therefore (X0 + 0x70), i.e., 0x1_3B88_B9D0. This + is indeed the value held in the FAR register. + +- The faulting address 0x1_3B88_B9D0 falls in the above-noted page (at + 0x1_3B88_B000), namely at offset 0x9D0. This is *beyond* the first 0x4F0 + bytes that the very tail of the "video_fb" module occupies at the front + of that page. + +For now, add a self-check that reports this bug (and prevents the crash by +skipping the write protection). + +Example log after the patch: + +> kern/dl.c:742:BUG: trying to protect pages outside of module allocation +> ("video_fb"): module base 0x13b87d000, size 0xe4f0; tramp/GOT base +> 0x13b88b000, size 0x1000 + +Signed-off-by: Laszlo Ersek +--- + grub-core/kern/dl.c | 11 ++++++++++- + 1 file changed, 10 insertions(+), 1 deletion(-) + +diff --git a/grub-core/kern/dl.c b/grub-core/kern/dl.c +index a97f4a8b13..3b66fa410e 100644 +--- a/grub-core/kern/dl.c ++++ b/grub-core/kern/dl.c +@@ -682,7 +682,7 @@ grub_dl_set_mem_attrs (grub_dl_t mod, void *ehdr) + #if !defined (__i386__) && !defined (__x86_64__) && !defined(__riscv) + grub_size_t arch_addralign = grub_arch_dl_min_alignment (); + grub_addr_t tgaddr; +- grub_uint64_t tgsz; ++ grub_size_t tgsz; + #endif + + grub_dprintf ("modules", "updating memory attributes for \"%s\"\n", +@@ -736,6 +736,15 @@ grub_dl_set_mem_attrs (grub_dl_t mod, void *ehdr) + grub_dprintf ("modules", + "updating attributes for GOT and trampolines (\"%s\")\n", + mod->name); ++ if (tgaddr < (grub_addr_t)mod->base || ++ tgsz > (grub_addr_t)-1 - tgaddr || ++ tgaddr + tgsz > (grub_addr_t)mod->base + mod->sz) ++ return grub_error (GRUB_ERR_BUG, ++ "BUG: trying to protect pages outside of module " ++ "allocation (\"%s\"): module base %p, size 0x%" ++ PRIxGRUB_SIZE "; tramp/GOT base 0x%" PRIxGRUB_ADDR ++ ", size 0x%" PRIxGRUB_SIZE, ++ mod->name, mod->base, mod->sz, tgaddr, tgsz); + grub_update_mem_attrs (tgaddr, tgsz, GRUB_MEM_ATTR_R|GRUB_MEM_ATTR_X, + GRUB_MEM_ATTR_W); + } diff --git a/0331-grub_dl_load_segments-page-align-the-tramp-GOT-areas.patch b/0331-grub_dl_load_segments-page-align-the-tramp-GOT-areas.patch new file mode 100644 index 0000000..f29609d --- /dev/null +++ b/0331-grub_dl_load_segments-page-align-the-tramp-GOT-areas.patch @@ -0,0 +1,70 @@ +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 +From: Laszlo Ersek +Date: Fri, 7 Apr 2023 16:56:09 +0200 +Subject: [PATCH] grub_dl_load_segments(): page-align the tramp/GOT areas too + +The tramp/GOT write-protection in grub_dl_set_mem_attrs() requires that +the tramp/GOT areas of the module image *not* share a page with any other +memory allocations. Page-align the tramp/GOT areas, while satisfying their +intrinsic alignment requirements too. + +Fixes: 887f1d8fa976 (modules: load module sections at page-aligned addresses) +Fixes: ad1b904d325b (nx: set page permissions for loaded modules.) +Signed-off-by: Laszlo Ersek +--- + grub-core/kern/dl.c | 24 ++++++++++++++++-------- + 1 file changed, 16 insertions(+), 8 deletions(-) + +diff --git a/grub-core/kern/dl.c b/grub-core/kern/dl.c +index 3b66fa410e..f3cdb9e0ba 100644 +--- a/grub-core/kern/dl.c ++++ b/grub-core/kern/dl.c +@@ -280,7 +280,9 @@ grub_dl_load_segments (grub_dl_t mod, const Elf_Ehdr *e) + grub_size_t tsize = 0, talign = 1, arch_addralign = 1; + #if !defined (__i386__) && !defined (__x86_64__) && !defined(__riscv) + grub_size_t tramp; ++ grub_size_t tramp_align; + grub_size_t got; ++ grub_size_t got_align; + grub_err_t err; + #endif + char *ptr; +@@ -311,12 +313,18 @@ grub_dl_load_segments (grub_dl_t mod, const Elf_Ehdr *e) + err = grub_arch_dl_get_tramp_got_size (e, &tramp, &got); + if (err) + return err; +- tsize += ALIGN_UP (tramp, GRUB_ARCH_DL_TRAMP_ALIGN); +- if (talign < GRUB_ARCH_DL_TRAMP_ALIGN) +- talign = GRUB_ARCH_DL_TRAMP_ALIGN; +- tsize += ALIGN_UP (got, GRUB_ARCH_DL_GOT_ALIGN); +- if (talign < GRUB_ARCH_DL_GOT_ALIGN) +- talign = GRUB_ARCH_DL_GOT_ALIGN; ++ tramp_align = GRUB_ARCH_DL_TRAMP_ALIGN; ++ if (tramp_align < arch_addralign) ++ tramp_align = arch_addralign; ++ tsize += ALIGN_UP (tramp, tramp_align); ++ if (talign < tramp_align) ++ talign = tramp_align; ++ got_align = GRUB_ARCH_DL_GOT_ALIGN; ++ if (got_align < arch_addralign) ++ got_align = arch_addralign; ++ tsize += ALIGN_UP (got, got_align); ++ if (talign < got_align) ++ talign = got_align; + #endif + + #ifdef GRUB_MACHINE_EMU +@@ -376,11 +384,11 @@ grub_dl_load_segments (grub_dl_t mod, const Elf_Ehdr *e) + } + } + #if !defined (__i386__) && !defined (__x86_64__) && !defined(__riscv) +- ptr = (char *) ALIGN_UP ((grub_addr_t) ptr, GRUB_ARCH_DL_TRAMP_ALIGN); ++ ptr = (char *) ALIGN_UP ((grub_addr_t) ptr, tramp_align); + mod->tramp = ptr; + mod->trampptr = ptr; + ptr += tramp; +- ptr = (char *) ALIGN_UP ((grub_addr_t) ptr, GRUB_ARCH_DL_GOT_ALIGN); ++ ptr = (char *) ALIGN_UP ((grub_addr_t) ptr, got_align); + mod->got = ptr; + mod->gotptr = ptr; + ptr += got; diff --git a/grub.patches b/grub.patches index 10c552f..0781c1b 100644 --- a/grub.patches +++ b/grub.patches @@ -326,3 +326,6 @@ Patch0325: 0325-emu-linux-work-around-systemctl-kexec-returning.patch Patch0326: 0326-kern-ieee1275-init-Convert-plain-numbers-to-constant.patch Patch0327: 0327-kern-ieee1275-init-Extended-support-in-Vec5.patch Patch0328: 0328-tpm-Disable-the-tpm-verifier-if-the-TPM-device-is-no.patch +Patch0329: 0329-grub_dl_set_mem_attrs-fix-format-string.patch +Patch0330: 0330-grub_dl_set_mem_attrs-add-self-check-for-the-tramp-G.patch +Patch0331: 0331-grub_dl_load_segments-page-align-the-tramp-GOT-areas.patch diff --git a/grub2.spec b/grub2.spec index 7a3bad6..34fdfe3 100644 --- a/grub2.spec +++ b/grub2.spec @@ -17,7 +17,7 @@ Name: grub2 Epoch: 1 Version: 2.06 -Release: 93%{?dist} +Release: 94%{?dist} Summary: Bootloader with support for Linux, Multiboot and more License: GPLv3+ URL: http://www.gnu.org/software/grub/ @@ -544,6 +544,9 @@ mv ${EFI_HOME}/grub.cfg.stb ${EFI_HOME}/grub.cfg %endif %changelog +* Mon Apr 10 2023 Robbie Harwood - 2.06-94 +- Fix aa64 page fault with EFI_MEMORY_ATTRIBUTE_PROTOCOL + * Fri Mar 31 2023 Robbie Harwood - 2.06-93 - Add legacy pxe core.0 (cmadams)