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Date: Wed, 2 Dec 2020 08:55:14 +0000
From: Szabolcs Nagy <szabolcs.nagy@....com>
To: libc-alpha@...rceware.org
Cc: Mark Rutland <mark.rutland@....com>,
kernel-hardening@...ts.openwall.com,
Catalin Marinas <catalin.marinas@....com>,
linux-kernel@...r.kernel.org,
Jeremy Linton <jeremy.linton@....com>,
Mark Brown <broonie@...nel.org>,
Topi Miettinen <toiwoton@...il.com>,
Will Deacon <will@...nel.org>,
linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v3 1/2] aarch64: align address for BTI protection [BZ #26988]
Handle unaligned executable load segments (the bfd linker is not
expected to produce such binaries, but other linkers may).
Computing the mapping bounds follows _dl_map_object_from_fd more
closely now.
Fixes bug 26988.
---
v3:
- split the last patch in two so this bug is fixed separately.
- pushed to nsz/btifix-v3 branch.
sysdeps/aarch64/dl-bti.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/sysdeps/aarch64/dl-bti.c b/sysdeps/aarch64/dl-bti.c
index 8f4728adce..67d63c8a73 100644
--- a/sysdeps/aarch64/dl-bti.c
+++ b/sysdeps/aarch64/dl-bti.c
@@ -20,19 +20,22 @@
#include <libintl.h>
#include <ldsodefs.h>
-static int
+static void
enable_bti (struct link_map *map, const char *program)
{
+ const size_t pagesz = GLRO(dl_pagesize);
const ElfW(Phdr) *phdr;
- unsigned prot;
for (phdr = map->l_phdr; phdr < &map->l_phdr[map->l_phnum]; ++phdr)
if (phdr->p_type == PT_LOAD && (phdr->p_flags & PF_X))
{
- void *start = (void *) (phdr->p_vaddr + map->l_addr);
- size_t len = phdr->p_memsz;
+ size_t vstart = ALIGN_DOWN (phdr->p_vaddr, pagesz);
+ size_t vend = ALIGN_UP (phdr->p_vaddr + phdr->p_filesz, pagesz);
+ off_t off = ALIGN_DOWN (phdr->p_offset, pagesz);
+ void *start = (void *) (vstart + map->l_addr);
+ size_t len = vend - vstart;
- prot = PROT_EXEC | PROT_BTI;
+ unsigned prot = PROT_EXEC | PROT_BTI;
if (phdr->p_flags & PF_R)
prot |= PROT_READ;
if (phdr->p_flags & PF_W)
@@ -48,7 +51,6 @@ enable_bti (struct link_map *map, const char *program)
N_("mprotect failed to turn on BTI"));
}
}
- return 0;
}
/* Enable BTI for MAP and its dependencies. */
--
2.17.1
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