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Properly compute offsets of note descriptor and next note [BZ #22370]
A note header has 3 4-bytes fields, followed by note name and note descriptor. According to gABI, in a note entry, the note name field, not note name size, is padded for the note descriptor. And the note descriptor field, not note descriptor size, is padded for the next note entry. Notes are aligned to 4 bytes in 32-bit objects and 8 bytes in 64-bit objects. For all GNU notes, the name is "GNU" which is 4 bytes. They have the same format in the first 16 bytes in both 32-bit and 64-bit objects. They differ by note descriptor size and note type. So far, .note.ABI-tag and .note.gnu.build-id notes are always aligned to 4 bytes. The exsting codes compute the note size by aligning the note name size and note descriptor size to 4 bytes. It happens to produce the same value as the actual note size by luck since the name size is 4 and offset of the note descriptor is 16. But it will produce the wrong size when note alignment is 8 bytes in 64-bit objects. This patch defines ELF_NOTE_DESC_OFFSET and ELF_NOTE_NEXT_OFFSET to properly compute offsets of note descriptor and next note. It uses alignment of PT_NOTE segment to support both 4-byte and 8-byte note alignments in 64-bit objects. To handle PT_NOTE segments with incorrect alignment, which may lead to an infinite loop, if segment alignment is less than 4, we treate alignment as 4 bytes since some note segments have 0 or 1 byte alignment. [BZ #22370] * elf/dl-hwcaps.c (ROUND): Removed. (_dl_important_hwcaps): Replace ROUND with ELF_NOTE_DESC_OFFSET and ELF_NOTE_NEXT_OFFSET. * elf/dl-load.c (ROUND): Removed. (open_verify): Replace ROUND with ELF_NOTE_NEXT_OFFSET. * elf/readelflib.c (ROUND): Removed. (process_elf_file): Replace ROUND with ELF_NOTE_NEXT_OFFSET. * include/elf.h [!_ISOMAC]: Include <libc-pointer-arith.h>. [!_ISOMAC] (ELF_NOTE_DESC_OFFSET): New. [!_ISOMAC] (ELF_NOTE_NEXT_OFFSET): Likewise.
This commit is contained in:
H.J. Lu
parent
313ba4630f
commit
8d81ce0c6d
14
ChangeLog
14
ChangeLog
@ -1,3 +1,17 @@
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2017-11-28 H.J. Lu <hongjiu.lu@intel.com>
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[BZ #22370]
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* elf/dl-hwcaps.c (ROUND): Removed.
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(_dl_important_hwcaps): Replace ROUND with ELF_NOTE_DESC_OFFSET
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and ELF_NOTE_NEXT_OFFSET.
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* elf/dl-load.c (ROUND): Removed.
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(open_verify): Replace ROUND with ELF_NOTE_NEXT_OFFSET.
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* elf/readelflib.c (ROUND): Removed.
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(process_elf_file): Replace ROUND with ELF_NOTE_NEXT_OFFSET.
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* include/elf.h [!_ISOMAC]: Include <libc-pointer-arith.h>.
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[!_ISOMAC] (ELF_NOTE_DESC_OFFSET): New.
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[!_ISOMAC] (ELF_NOTE_NEXT_OFFSET): Likewise.
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2017-11-28 Joseph Myers <joseph@codesourcery.com>
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* sysdeps/s390/fpu/s_fmaf.c: Include <libm-alias-float.h>.
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@ -67,6 +67,18 @@ _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz,
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{
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const ElfW(Addr) start = (phdr[i].p_vaddr
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+ GLRO(dl_sysinfo_map)->l_addr);
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/* NB: Some PT_NOTE segment may have alignment value of 0
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or 1. gABI specifies that PT_NOTE segments should be
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aligned to 4 bytes in 32-bit objects and to 8 bytes in
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64-bit objects. As a Linux extension, we also support
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4 byte alignment in 64-bit objects. If p_align is less
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than 4, we treate alignment as 4 bytes since some note
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segments have 0 or 1 byte alignment. */
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ElfW(Addr) align = phdr[i].p_align;
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if (align < 4)
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align = 4;
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else if (align != 4 && align != 8)
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continue;
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/* The standard ELF note layout is exactly as the anonymous struct.
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The next element is a variable length vendor name of length
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VENDORLEN (with a real length rounded to ElfW(Word)), followed
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@ -80,7 +92,6 @@ _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz,
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} *note = (const void *) start;
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while ((ElfW(Addr)) (note + 1) - start < phdr[i].p_memsz)
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{
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#define ROUND(len) (((len) + sizeof (ElfW(Word)) - 1) & -sizeof (ElfW(Word)))
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/* The layout of the type 2, vendor "GNU" note is as follows:
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.long <Number of capabilities enabled by this note>
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.long <Capabilities mask> (as mask >> _DL_FIRST_EXTRA).
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@ -91,17 +102,18 @@ _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz,
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&& !memcmp ((note + 1), "GNU", sizeof "GNU")
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&& note->datalen > 2 * sizeof (ElfW(Word)) + 2)
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{
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const ElfW(Word) *p = ((const void *) (note + 1)
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+ ROUND (sizeof "GNU"));
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const ElfW(Word) *p
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= ((const void *) note
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+ ELF_NOTE_DESC_OFFSET (sizeof "GNU", align));
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cnt += *p++;
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++p; /* Skip mask word. */
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dsocaps = (const char *) p; /* Pseudo-string "<b>name" */
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dsocapslen = note->datalen - sizeof *p * 2;
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break;
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}
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note = ((const void *) (note + 1)
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+ ROUND (note->vendorlen) + ROUND (note->datalen));
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#undef ROUND
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note = ((const void *) note
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+ ELF_NOTE_NEXT_OFFSET (note->vendorlen,
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note->datalen, align));
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}
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if (dsocaps != NULL)
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break;
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@ -1683,6 +1683,18 @@ open_verify (const char *name, int fd,
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if (ph->p_type == PT_NOTE && ph->p_filesz >= 32 && ph->p_align >= 4)
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{
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ElfW(Addr) size = ph->p_filesz;
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/* NB: Some PT_NOTE segment may have alignment value of 0
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or 1. gABI specifies that PT_NOTE segments should be
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aligned to 4 bytes in 32-bit objects and to 8 bytes in
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64-bit objects. As a Linux extension, we also support
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4 byte alignment in 64-bit objects. If p_align is less
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than 4, we treate alignment as 4 bytes since some note
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segments have 0 or 1 byte alignment. */
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ElfW(Addr) align = ph->p_align;
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if (align < 4)
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align = 4;
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else if (align != 4 && align != 8)
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continue;
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if (ph->p_offset + size <= (size_t) fbp->len)
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abi_note = (void *) (fbp->buf + ph->p_offset);
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@ -1696,10 +1708,9 @@ open_verify (const char *name, int fd,
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while (memcmp (abi_note, &expected_note, sizeof (expected_note)))
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{
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#define ROUND(len) (((len) + sizeof (ElfW(Word)) - 1) & -sizeof (ElfW(Word)))
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ElfW(Addr) note_size = 3 * sizeof (ElfW(Word))
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+ ROUND (abi_note[0])
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+ ROUND (abi_note[1]);
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ElfW(Addr) note_size
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= ELF_NOTE_NEXT_OFFSET (abi_note[0], abi_note[1],
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align);
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if (size - 32 < note_size)
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{
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@ -131,15 +131,26 @@ process_elf_file (const char *file_name, const char *lib, int *flag,
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ElfW(Word) *abi_note = (ElfW(Word) *) (file_contents
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+ segment->p_offset);
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ElfW(Addr) size = segment->p_filesz;
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/* NB: Some PT_NOTE segment may have alignment value of 0
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or 1. gABI specifies that PT_NOTE segments should be
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aligned to 4 bytes in 32-bit objects and to 8 bytes in
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64-bit objects. As a Linux extension, we also support
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4 byte alignment in 64-bit objects. If p_align is less
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than 4, we treate alignment as 4 bytes since some note
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segments have 0 or 1 byte alignment. */
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ElfW(Addr) align = segment->p_align;
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if (align < 4)
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align = 4;
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else if (align != 4 && align != 8)
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continue;
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while (abi_note [0] != 4 || abi_note [1] != 16
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|| abi_note [2] != 1
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|| memcmp (abi_note + 3, "GNU", 4) != 0)
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{
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#define ROUND(len) (((len) + sizeof (ElfW(Word)) - 1) & -sizeof (ElfW(Word)))
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ElfW(Addr) note_size = 3 * sizeof (ElfW(Word))
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+ ROUND (abi_note[0])
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+ ROUND (abi_note[1]);
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ElfW(Addr) note_size
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= ELF_NOTE_NEXT_OFFSET (abi_note[0], abi_note[1],
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align);
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if (size - 32 < note_size || note_size == 0)
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{
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@ -1,7 +1,19 @@
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#ifndef _ELF_H
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#include <elf/elf.h>
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# ifndef _ISOMAC
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#ifndef _ISOMAC
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# include <libc-pointer-arith.h>
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/* Compute the offset of the note descriptor from size of note entry's
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owner string and note alignment. */
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# define ELF_NOTE_DESC_OFFSET(namesz, align) \
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ALIGN_UP (sizeof (ElfW(Nhdr)) + (namesz), (align))
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/* Compute the offset of the next note entry from size of note entry's
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owner string, size of the note descriptor and note alignment. */
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# define ELF_NOTE_NEXT_OFFSET(namesz, descsz, align) \
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ALIGN_UP (ELF_NOTE_DESC_OFFSET ((namesz), (align)) + (descsz), (align))
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/* Some information which is not meant for the public and therefore not
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in <elf.h>. */
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@ -13,5 +25,5 @@
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(DF_1_NOW | DF_1_NODELETE | DF_1_INITFIRST | DF_1_NOOPEN \
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| DF_1_ORIGIN | DF_1_NODEFLIB)
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# endif /* !_ISOMAC */
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#endif /* !_ISOMAC */
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#endif /* elf.h */
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