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Fix aa64 page fault with EFI_MEMORY_ATTRIBUTE_PROTOCOL
Signed-off-by: Robbie Harwood <rharwood@redhat.com>
This commit is contained in:
Robbie Harwood
parent
ab62564e2f
commit
e6b8f35a69
5 changed files with 255 additions and 1 deletions
38
0329-grub_dl_set_mem_attrs-fix-format-string.patch
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38
0329-grub_dl_set_mem_attrs-fix-format-string.patch
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@ -0,0 +1,38 @@
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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Laszlo Ersek <lersek@redhat.com>
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Date: Fri, 7 Apr 2023 14:54:35 +0200
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Subject: [PATCH] grub_dl_set_mem_attrs(): fix format string
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The grub_dprintf() call for printing the message
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updating attributes for GOT and trampolines
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passes the argument "mod->name", but the format string doesn't accept that
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argument.
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Print the module name too.
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Example output:
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> kern/dl.c:736: updating attributes for GOT and trampolines ("video_fb")
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Fixes: ad1b904d325b (nx: set page permissions for loaded modules.)
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Signed-off-by: Laszlo Ersek <lersek@redhat.com>
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---
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grub-core/kern/dl.c | 3 ++-
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1 file changed, 2 insertions(+), 1 deletion(-)
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diff --git a/grub-core/kern/dl.c b/grub-core/kern/dl.c
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index ab9101a5ad..a97f4a8b13 100644
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--- a/grub-core/kern/dl.c
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+++ b/grub-core/kern/dl.c
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@@ -733,7 +733,8 @@ grub_dl_set_mem_attrs (grub_dl_t mod, void *ehdr)
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{
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tgsz = ALIGN_UP(tgsz, arch_addralign);
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- grub_dprintf ("modules", "updating attributes for GOT and trampolines\n",
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+ grub_dprintf ("modules",
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+ "updating attributes for GOT and trampolines (\"%s\")\n",
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mod->name);
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grub_update_mem_attrs (tgaddr, tgsz, GRUB_MEM_ATTR_R|GRUB_MEM_ATTR_X,
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GRUB_MEM_ATTR_W);
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140
0330-grub_dl_set_mem_attrs-add-self-check-for-the-tramp-G.patch
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140
0330-grub_dl_set_mem_attrs-add-self-check-for-the-tramp-G.patch
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@ -0,0 +1,140 @@
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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Laszlo Ersek <lersek@redhat.com>
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Date: Fri, 7 Apr 2023 16:21:54 +0200
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Subject: [PATCH] grub_dl_set_mem_attrs(): add self-check for the tramp/GOT
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sizes
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On aarch64 UEFI, we currently have a crasher:
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grub_dl_load_core()
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grub_dl_load_core_noinit()
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/* independent allocation: must remain writable */
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mod = grub_zalloc();
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/* allocates module image with incorrect tail alignment */
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grub_dl_load_segments()
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/* write-protecting the module image makes "mod" read-only! */
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grub_dl_set_mem_attrs()
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grub_update_mem_attrs()
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grub_dl_init()
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/* page fault, crash */
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mod->next = ...;
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- Commit 887f1d8fa976 ("modules: load module sections at page-aligned
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addresses", 2023-02-08) forgot to page-align the allocation of the
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trampolines and GOT areas of grub2 modules, in grub_dl_load_segments().
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- Commit ad1b904d325b ("nx: set page permissions for loaded modules.",
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2023-02-08) calculated a common bounding box for the trampolines and GOT
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areas in grub_dl_set_mem_attrs(), rounded the box size up to a whole
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multiple of EFI page size ("arch_addralign"), and write-protected the
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resultant page range.
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Consequently, grub_dl_load_segments() places the module image in memory
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such that its tail -- the end of the trampolines and GOT areas -- lands at
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the head of a page whose tail in turn contains independent memory
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allocations, such as "mod". grub_dl_set_mem_attrs() will then unwittingly
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write-protect these other allocations too.
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But "mod" must remain writable: we assign "mod->next" in grub_dl_init()
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subsequently. Currently we crash there with a page fault / permission
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fault.
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(The crash is not trivial to hit: the tramp/GOT areas are irrelevant on
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x86_64, plus the page protection depends on the UEFI platform firmware
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providing EFI_MEMORY_ATTRIBUTE_PROTOCOL. In practice, the crash is
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restricted to aarch64 edk2 (ArmVirtQemu) builds containing commit
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1c4dfadb4611, "ArmPkg/CpuDxe: Implement EFI memory attributes protocol",
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2023-03-16.)
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Example log before the patch:
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> kern/dl.c:736: updating attributes for GOT and trampolines ("video_fb")
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> kern/efi/mm.c:927: set +rx -w on 0x13b88b000-0x13b88bfff before:rwx after:r-x
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> kern/dl.c:744: done updating module memory attributes for "video_fb"
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> kern/dl.c:639: flushing 0xe4f0 bytes at 0x13b87d000
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> kern/arm64/cache.c:42: D$ line size: 64
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> kern/arm64/cache.c:43: I$ line size: 64
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> kern/dl.c:839: module name: video_fb
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> kern/dl.c:840: init function: 0x0
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> kern/dl.c:865: Initing module video_fb
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>
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> Synchronous Exception at 0x000000013B8A76EC
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> PC 0x00013B8A76EC
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>
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> X0 0x000000013B88B960 X1 0x0000000000000000 X2 0x000000013F93587C X3 0x0000000000000075
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>
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> SP 0x00000000470745C0 ELR 0x000000013B8A76EC SPSR 0x60000205 FPSR 0x00000000
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> ESR 0x9600004F FAR 0x000000013B88B9D0
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>
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> ESR : EC 0x25 IL 0x1 ISS 0x0000004F
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>
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> Data abort: Permission fault, third level
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Note the following:
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- The whole 4K page at 0x1_3B88_B000 is write-protected.
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- The "video_fb" module actually lives at [0x1_3B87_D000, 0x1_3B88_B4F0)
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-- left-inclusive, right-exclusive --; that is, in the last page (at
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0x1_3B88_B000), it only occupies the first 0x4F0 bytes.
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- The instruction at 0x1_3B8A_76EC faults. Not shown here, but it is a
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store instruction, which writes to the field at offset 0x70 of the
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structure pointed-to by the X0 register. This is the "mod->next"
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assignment from grub_dl_init().
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- The faulting address is therefore (X0 + 0x70), i.e., 0x1_3B88_B9D0. This
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is indeed the value held in the FAR register.
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- The faulting address 0x1_3B88_B9D0 falls in the above-noted page (at
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0x1_3B88_B000), namely at offset 0x9D0. This is *beyond* the first 0x4F0
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bytes that the very tail of the "video_fb" module occupies at the front
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of that page.
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For now, add a self-check that reports this bug (and prevents the crash by
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skipping the write protection).
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Example log after the patch:
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> kern/dl.c:742:BUG: trying to protect pages outside of module allocation
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> ("video_fb"): module base 0x13b87d000, size 0xe4f0; tramp/GOT base
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> 0x13b88b000, size 0x1000
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Signed-off-by: Laszlo Ersek <lersek@redhat.com>
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---
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grub-core/kern/dl.c | 11 ++++++++++-
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1 file changed, 10 insertions(+), 1 deletion(-)
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diff --git a/grub-core/kern/dl.c b/grub-core/kern/dl.c
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index a97f4a8b13..3b66fa410e 100644
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--- a/grub-core/kern/dl.c
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+++ b/grub-core/kern/dl.c
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@@ -682,7 +682,7 @@ grub_dl_set_mem_attrs (grub_dl_t mod, void *ehdr)
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#if !defined (__i386__) && !defined (__x86_64__) && !defined(__riscv)
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grub_size_t arch_addralign = grub_arch_dl_min_alignment ();
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grub_addr_t tgaddr;
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- grub_uint64_t tgsz;
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+ grub_size_t tgsz;
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#endif
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grub_dprintf ("modules", "updating memory attributes for \"%s\"\n",
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@@ -736,6 +736,15 @@ grub_dl_set_mem_attrs (grub_dl_t mod, void *ehdr)
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grub_dprintf ("modules",
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"updating attributes for GOT and trampolines (\"%s\")\n",
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mod->name);
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+ if (tgaddr < (grub_addr_t)mod->base ||
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+ tgsz > (grub_addr_t)-1 - tgaddr ||
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+ tgaddr + tgsz > (grub_addr_t)mod->base + mod->sz)
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+ return grub_error (GRUB_ERR_BUG,
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+ "BUG: trying to protect pages outside of module "
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+ "allocation (\"%s\"): module base %p, size 0x%"
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+ PRIxGRUB_SIZE "; tramp/GOT base 0x%" PRIxGRUB_ADDR
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+ ", size 0x%" PRIxGRUB_SIZE,
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+ mod->name, mod->base, mod->sz, tgaddr, tgsz);
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grub_update_mem_attrs (tgaddr, tgsz, GRUB_MEM_ATTR_R|GRUB_MEM_ATTR_X,
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GRUB_MEM_ATTR_W);
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}
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@ -0,0 +1,70 @@
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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Laszlo Ersek <lersek@redhat.com>
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Date: Fri, 7 Apr 2023 16:56:09 +0200
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Subject: [PATCH] grub_dl_load_segments(): page-align the tramp/GOT areas too
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The tramp/GOT write-protection in grub_dl_set_mem_attrs() requires that
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the tramp/GOT areas of the module image *not* share a page with any other
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memory allocations. Page-align the tramp/GOT areas, while satisfying their
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intrinsic alignment requirements too.
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Fixes: 887f1d8fa976 (modules: load module sections at page-aligned addresses)
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Fixes: ad1b904d325b (nx: set page permissions for loaded modules.)
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Signed-off-by: Laszlo Ersek <lersek@redhat.com>
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---
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grub-core/kern/dl.c | 24 ++++++++++++++++--------
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1 file changed, 16 insertions(+), 8 deletions(-)
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diff --git a/grub-core/kern/dl.c b/grub-core/kern/dl.c
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index 3b66fa410e..f3cdb9e0ba 100644
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--- a/grub-core/kern/dl.c
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+++ b/grub-core/kern/dl.c
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@@ -280,7 +280,9 @@ grub_dl_load_segments (grub_dl_t mod, const Elf_Ehdr *e)
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grub_size_t tsize = 0, talign = 1, arch_addralign = 1;
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#if !defined (__i386__) && !defined (__x86_64__) && !defined(__riscv)
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grub_size_t tramp;
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+ grub_size_t tramp_align;
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grub_size_t got;
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+ grub_size_t got_align;
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grub_err_t err;
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#endif
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char *ptr;
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@@ -311,12 +313,18 @@ grub_dl_load_segments (grub_dl_t mod, const Elf_Ehdr *e)
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err = grub_arch_dl_get_tramp_got_size (e, &tramp, &got);
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if (err)
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return err;
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- tsize += ALIGN_UP (tramp, GRUB_ARCH_DL_TRAMP_ALIGN);
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- if (talign < GRUB_ARCH_DL_TRAMP_ALIGN)
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- talign = GRUB_ARCH_DL_TRAMP_ALIGN;
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- tsize += ALIGN_UP (got, GRUB_ARCH_DL_GOT_ALIGN);
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- if (talign < GRUB_ARCH_DL_GOT_ALIGN)
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- talign = GRUB_ARCH_DL_GOT_ALIGN;
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+ tramp_align = GRUB_ARCH_DL_TRAMP_ALIGN;
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+ if (tramp_align < arch_addralign)
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+ tramp_align = arch_addralign;
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+ tsize += ALIGN_UP (tramp, tramp_align);
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+ if (talign < tramp_align)
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+ talign = tramp_align;
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+ got_align = GRUB_ARCH_DL_GOT_ALIGN;
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+ if (got_align < arch_addralign)
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+ got_align = arch_addralign;
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+ tsize += ALIGN_UP (got, got_align);
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+ if (talign < got_align)
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+ talign = got_align;
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#endif
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#ifdef GRUB_MACHINE_EMU
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@@ -376,11 +384,11 @@ grub_dl_load_segments (grub_dl_t mod, const Elf_Ehdr *e)
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}
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}
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#if !defined (__i386__) && !defined (__x86_64__) && !defined(__riscv)
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- ptr = (char *) ALIGN_UP ((grub_addr_t) ptr, GRUB_ARCH_DL_TRAMP_ALIGN);
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+ ptr = (char *) ALIGN_UP ((grub_addr_t) ptr, tramp_align);
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mod->tramp = ptr;
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mod->trampptr = ptr;
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ptr += tramp;
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- ptr = (char *) ALIGN_UP ((grub_addr_t) ptr, GRUB_ARCH_DL_GOT_ALIGN);
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+ ptr = (char *) ALIGN_UP ((grub_addr_t) ptr, got_align);
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mod->got = ptr;
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mod->gotptr = ptr;
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ptr += got;
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@ -326,3 +326,6 @@ Patch0325: 0325-emu-linux-work-around-systemctl-kexec-returning.patch
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Patch0326: 0326-kern-ieee1275-init-Convert-plain-numbers-to-constant.patch
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Patch0327: 0327-kern-ieee1275-init-Extended-support-in-Vec5.patch
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Patch0328: 0328-tpm-Disable-the-tpm-verifier-if-the-TPM-device-is-no.patch
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Patch0329: 0329-grub_dl_set_mem_attrs-fix-format-string.patch
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Patch0330: 0330-grub_dl_set_mem_attrs-add-self-check-for-the-tramp-G.patch
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Patch0331: 0331-grub_dl_load_segments-page-align-the-tramp-GOT-areas.patch
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@ -17,7 +17,7 @@
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Name: grub2
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Epoch: 1
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Version: 2.06
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Release: 93%{?dist}
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Release: 94%{?dist}
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Summary: Bootloader with support for Linux, Multiboot and more
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License: GPLv3+
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URL: http://www.gnu.org/software/grub/
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@ -544,6 +544,9 @@ mv ${EFI_HOME}/grub.cfg.stb ${EFI_HOME}/grub.cfg
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%endif
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%changelog
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* Mon Apr 10 2023 Robbie Harwood <rharwood@redhat.com> - 2.06-94
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- Fix aa64 page fault with EFI_MEMORY_ATTRIBUTE_PROTOCOL
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* Fri Mar 31 2023 Robbie Harwood <rharwood@redhat.com> - 2.06-93
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- Add legacy pxe core.0 (cmadams)
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