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Message-ID: <alpine.DEB.2.00.0910190422090.13303@andre.icculuslan>
Date: Mon, 19 Oct 2009 10:41:22 -0400 (EDT)
From: "Ryan C. Gordon" <icculus@...ulus.org>
To: linux-kernel@...r.kernel.org
Subject: [RFC][PATCH 2/2] binfmt_elf: FatELF support for kernel modules.
Allows kernel modules to be FatELF binaries.
Details, rationale, tools, and patches for handling FatELF binaries can be
found at http://icculus.org/fatelf/
Please note that this requires an updated depmod and modprobe to be truly
effective, but an unmodified insmod can work with FatELF binaries.
Signed-off-by: Ryan C. Gordon <icculus@...ulus.org>
---
kernel/module.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++----
1 files changed, 67 insertions(+), 5 deletions(-)
diff --git a/kernel/module.c b/kernel/module.c
index 8b7d880..cda8f79 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2066,13 +2066,69 @@ static inline void kmemleak_load_module(struct module *mod, Elf_Ehdr *hdr,
}
#endif
+/*
+ * See if we're a valid FatELF binary, find the right record, and
+ * return the offset of that record within the binary. Returns NULL if there's
+ * a problem, or a pointer to the real ELF header if we're okay.
+ * If we don't see the FatELF magic number, we assume this is a regular ELF
+ * binary and let the regular ELF checks handle it.
+ *
+ * This is a simplified version of examine_fatelf in fs/binfmt_elf.c
+ */
+static Elf_Ehdr *examine_fatelf_module(const unsigned char *hdr,
+ const unsigned long len)
+{
+ Elf_Ehdr elf;
+ int records, i;
+ const fatelf_hdr *fatelf = (const fatelf_hdr *) hdr;
+
+ if (likely(le32_to_cpu(fatelf->magic) != FATELF_MAGIC)) {
+ return (Elf_Ehdr *) hdr; /* not FatELF; not an error. */
+ } else if (unlikely(le16_to_cpu(fatelf->version) != 1)) {
+ return NULL; /* Unrecognized format version. */
+ }
+
+ memset(&elf, 0, sizeof (elf));
+
+ records = (int) fatelf->num_records; /* uint8, no byteswap needed */
+ for (i = 0; i < records; i++) {
+ const fatelf_record *record = &fatelf->records[i];
+
+ /* Fill in the data elf_check_arch() might care about. */
+ elf.e_ident[EI_OSABI] = record->osabi;
+ elf.e_ident[EI_CLASS] = record->word_size;
+ elf.e_ident[EI_DATA] = record->byte_order;
+ elf.e_machine = le16_to_cpu(record->machine);
+
+ if (likely(!elf_check_arch(&elf))) {
+ continue; /* Unsupported CPU architecture. */
+ } else {
+ const __u64 rec_offset = le64_to_cpu(record->offset);
+ const __u64 rec_size = le64_to_cpu(record->size);
+ const __u64 end_offset = rec_offset + rec_size;
+ const unsigned long uloff = (unsigned long) rec_offset;
+
+ if (unlikely(end_offset < rec_offset)) {
+ continue; /* overflow (corrupt file?)... */
+ } else if (unlikely(end_offset > len)) {
+ continue; /* past EOF. */
+ }
+
+ return (Elf_Ehdr *) (hdr + uloff);
+ }
+ }
+
+ return NULL; /* no binaries we could use. */
+}
+
/* Allocate and load the module: note that size of section 0 is always
zero, and we rely on this for optional sections. */
static noinline struct module *load_module(void __user *umod,
unsigned long len,
const char __user *uargs)
{
- Elf_Ehdr *hdr;
+ Elf_Ehdr *hdr_alloc; /* returned from vmalloc */
+ Elf_Ehdr *hdr; /* adjusted hdr_alloc for FatELF */
Elf_Shdr *sechdrs;
char *secstrings, *args, *modmagic, *strtab = NULL;
char *staging;
@@ -2094,14 +2150,20 @@ static noinline struct module *load_module(void __user *umod,
/* Suck in entire file: we'll want most of it. */
/* vmalloc barfs on "unusual" numbers. Check here */
- if (len > 64 * 1024 * 1024 || (hdr = vmalloc(len)) == NULL)
+ if (len > 64 * 1024 * 1024 || (hdr_alloc = vmalloc(len)) == NULL)
return ERR_PTR(-ENOMEM);
- if (copy_from_user(hdr, umod, len) != 0) {
+ if (copy_from_user(hdr_alloc, umod, len) != 0) {
err = -EFAULT;
goto free_hdr;
}
+ hdr = examine_fatelf_module((unsigned char *) hdr_alloc, len);
+ if (hdr == NULL) {
+ err = -ENOEXEC;
+ goto free_hdr;
+ }
+
/* Sanity checks against insmoding binaries or wrong arch,
weird elf version */
if (memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0
@@ -2505,7 +2567,7 @@ static noinline struct module *load_module(void __user *umod,
add_notes_attrs(mod, hdr->e_shnum, secstrings, sechdrs);
/* Get rid of temporary copy */
- vfree(hdr);
+ vfree(hdr_alloc);
trace_module_load(mod);
@@ -2538,7 +2600,7 @@ static noinline struct module *load_module(void __user *umod,
kfree(args);
kfree(strmap);
free_hdr:
- vfree(hdr);
+ vfree(hdr_alloc);
return ERR_PTR(err);
truncated:
--
1.6.0.4
--
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