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coredump: Snapshot the vmas in do_coredump
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Move the call of dump_vma_snapshot and kvfree(vma_meta) out of the
individual coredump routines into do_coredump itself.  This makes
the code less error prone and easier to maintain.

Make the vma snapshot available to the coredump routines
in struct coredump_params.  This makes it easier to
change and update what is captures in the vma snapshot
and will be needed for fixing fill_file_notes.

Reviewed-by: Jann Horn <jannh@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Eric W. Biederman committed Mar 8, 2022
1 parent a99a3e2 commit 95c5436
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Showing 4 changed files with 39 additions and 46 deletions.
20 changes: 7 additions & 13 deletions fs/binfmt_elf.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2191,25 +2191,20 @@ static void fill_extnum_info(struct elfhdr *elf, struct elf_shdr *shdr4extnum,
static int elf_core_dump(struct coredump_params *cprm)
{
int has_dumped = 0;
int vma_count, segs, i;
size_t vma_data_size;
int segs, i;
struct elfhdr elf;
loff_t offset = 0, dataoff;
struct elf_note_info info = { };
struct elf_phdr *phdr4note = NULL;
struct elf_shdr *shdr4extnum = NULL;
Elf_Half e_phnum;
elf_addr_t e_shoff;
struct core_vma_metadata *vma_meta;

if (dump_vma_snapshot(cprm, &vma_count, &vma_meta, &vma_data_size))
return 0;

/*
* The number of segs are recored into ELF header as 16bit value.
* Please check DEFAULT_MAX_MAP_COUNT definition when you modify here.
*/
segs = vma_count + elf_core_extra_phdrs();
segs = cprm->vma_count + elf_core_extra_phdrs();

/* for notes section */
segs++;
Expand Down Expand Up @@ -2248,7 +2243,7 @@ static int elf_core_dump(struct coredump_params *cprm)

dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);

offset += vma_data_size;
offset += cprm->vma_data_size;
offset += elf_core_extra_data_size();
e_shoff = offset;

Expand All @@ -2268,8 +2263,8 @@ static int elf_core_dump(struct coredump_params *cprm)
goto end_coredump;

/* Write program headers for segments dump */
for (i = 0; i < vma_count; i++) {
struct core_vma_metadata *meta = vma_meta + i;
for (i = 0; i < cprm->vma_count; i++) {
struct core_vma_metadata *meta = cprm->vma_meta + i;
struct elf_phdr phdr;

phdr.p_type = PT_LOAD;
Expand Down Expand Up @@ -2306,8 +2301,8 @@ static int elf_core_dump(struct coredump_params *cprm)
/* Align to page */
dump_skip_to(cprm, dataoff);

for (i = 0; i < vma_count; i++) {
struct core_vma_metadata *meta = vma_meta + i;
for (i = 0; i < cprm->vma_count; i++) {
struct core_vma_metadata *meta = cprm->vma_meta + i;

if (!dump_user_range(cprm, meta->start, meta->dump_size))
goto end_coredump;
Expand All @@ -2324,7 +2319,6 @@ static int elf_core_dump(struct coredump_params *cprm)
end_coredump:
free_note_info(&info);
kfree(shdr4extnum);
kvfree(vma_meta);
kfree(phdr4note);
return has_dumped;
}
Expand Down
18 changes: 6 additions & 12 deletions fs/binfmt_elf_fdpic.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1465,7 +1465,7 @@ static bool elf_fdpic_dump_segments(struct coredump_params *cprm,
static int elf_fdpic_core_dump(struct coredump_params *cprm)
{
int has_dumped = 0;
int vma_count, segs;
int segs;
int i;
struct elfhdr *elf = NULL;
loff_t offset = 0, dataoff;
Expand All @@ -1480,8 +1480,6 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
elf_addr_t e_shoff;
struct core_thread *ct;
struct elf_thread_status *tmp;
struct core_vma_metadata *vma_meta = NULL;
size_t vma_data_size;

/* alloc memory for large data structures: too large to be on stack */
elf = kmalloc(sizeof(*elf), GFP_KERNEL);
Expand All @@ -1491,9 +1489,6 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
if (!psinfo)
goto end_coredump;

if (dump_vma_snapshot(cprm, &vma_count, &vma_meta, &vma_data_size))
goto end_coredump;

for (ct = current->signal->core_state->dumper.next;
ct; ct = ct->next) {
tmp = elf_dump_thread_status(cprm->siginfo->si_signo,
Expand All @@ -1513,7 +1508,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
tmp->next = thread_list;
thread_list = tmp;

segs = vma_count + elf_core_extra_phdrs();
segs = cprm->vma_count + elf_core_extra_phdrs();

/* for notes section */
segs++;
Expand Down Expand Up @@ -1558,7 +1553,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
/* Page-align dumped data */
dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);

offset += vma_data_size;
offset += cprm->vma_data_size;
offset += elf_core_extra_data_size();
e_shoff = offset;

Expand All @@ -1578,8 +1573,8 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
goto end_coredump;

/* write program headers for segments dump */
for (i = 0; i < vma_count; i++) {
struct core_vma_metadata *meta = vma_meta + i;
for (i = 0; i < cprm->vma_count; i++) {
struct core_vma_metadata *meta = cprm->vma_meta + i;
struct elf_phdr phdr;
size_t sz;

Expand Down Expand Up @@ -1628,7 +1623,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)

dump_skip_to(cprm, dataoff);

if (!elf_fdpic_dump_segments(cprm, vma_meta, vma_count))
if (!elf_fdpic_dump_segments(cprm, cprm->vma_meta, cprm->vma_count))
goto end_coredump;

if (!elf_core_write_extra_data(cprm))
Expand All @@ -1652,7 +1647,6 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
thread_list = thread_list->next;
kfree(tmp);
}
kvfree(vma_meta);
kfree(phdr4note);
kfree(elf);
kfree(psinfo);
Expand Down
41 changes: 23 additions & 18 deletions fs/coredump.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,8 @@

#include <trace/events/sched.h>

static bool dump_vma_snapshot(struct coredump_params *cprm);

static int core_uses_pid;
static unsigned int core_pipe_limit;
static char core_pattern[CORENAME_MAX_SIZE] = "core";
Expand Down Expand Up @@ -532,6 +534,7 @@ void do_coredump(const kernel_siginfo_t *siginfo)
* by any locks.
*/
.mm_flags = mm->flags,
.vma_meta = NULL,
};

audit_core_dumps(siginfo->si_signo);
Expand Down Expand Up @@ -746,6 +749,9 @@ void do_coredump(const kernel_siginfo_t *siginfo)
pr_info("Core dump to |%s disabled\n", cn.corename);
goto close_fail;
}
if (!dump_vma_snapshot(&cprm))
goto close_fail;

file_start_write(cprm.file);
core_dumped = binfmt->core_dump(&cprm);
/*
Expand All @@ -759,6 +765,7 @@ void do_coredump(const kernel_siginfo_t *siginfo)
dump_emit(&cprm, "", 1);
}
file_end_write(cprm.file);
kvfree(cprm.vma_meta);
}
if (ispipe && core_pipe_limit)
wait_for_dump_helpers(cprm.file);
Expand Down Expand Up @@ -1096,35 +1103,33 @@ static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
* Under the mmap_lock, take a snapshot of relevant information about the task's
* VMAs.
*/
int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
struct core_vma_metadata **vma_meta,
size_t *vma_data_size_ptr)
static bool dump_vma_snapshot(struct coredump_params *cprm)
{
struct vm_area_struct *vma, *gate_vma;
struct mm_struct *mm = current->mm;
int i;
size_t vma_data_size = 0;

/*
* Once the stack expansion code is fixed to not change VMA bounds
* under mmap_lock in read mode, this can be changed to take the
* mmap_lock in read mode.
*/
if (mmap_write_lock_killable(mm))
return -EINTR;
return false;

cprm->vma_data_size = 0;
gate_vma = get_gate_vma(mm);
*vma_count = mm->map_count + (gate_vma ? 1 : 0);
cprm->vma_count = mm->map_count + (gate_vma ? 1 : 0);

*vma_meta = kvmalloc_array(*vma_count, sizeof(**vma_meta), GFP_KERNEL);
if (!*vma_meta) {
cprm->vma_meta = kvmalloc_array(cprm->vma_count, sizeof(*cprm->vma_meta), GFP_KERNEL);
if (!cprm->vma_meta) {
mmap_write_unlock(mm);
return -ENOMEM;
return false;
}

for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
vma = next_vma(vma, gate_vma), i++) {
struct core_vma_metadata *m = (*vma_meta) + i;
struct core_vma_metadata *m = cprm->vma_meta + i;

m->start = vma->vm_start;
m->end = vma->vm_end;
Expand All @@ -1134,13 +1139,14 @@ int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,

mmap_write_unlock(mm);

if (WARN_ON(i != *vma_count)) {
kvfree(*vma_meta);
return -EFAULT;
if (WARN_ON(i != cprm->vma_count)) {
kvfree(cprm->vma_meta);
return false;
}

for (i = 0; i < *vma_count; i++) {
struct core_vma_metadata *m = (*vma_meta) + i;

for (i = 0; i < cprm->vma_count; i++) {
struct core_vma_metadata *m = cprm->vma_meta + i;

if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) {
char elfmag[SELFMAG];
Expand All @@ -1153,9 +1159,8 @@ int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
}
}

vma_data_size += m->dump_size;
cprm->vma_data_size += m->dump_size;
}

*vma_data_size_ptr = vma_data_size;
return 0;
return true;
}
6 changes: 3 additions & 3 deletions include/linux/coredump.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,9 @@ struct coredump_params {
loff_t written;
loff_t pos;
loff_t to_skip;
int vma_count;
size_t vma_data_size;
struct core_vma_metadata *vma_meta;
};

/*
Expand All @@ -35,9 +38,6 @@ extern int dump_emit(struct coredump_params *cprm, const void *addr, int nr);
extern int dump_align(struct coredump_params *cprm, int align);
int dump_user_range(struct coredump_params *cprm, unsigned long start,
unsigned long len);
int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
struct core_vma_metadata **vma_meta,
size_t *vma_data_size_ptr);
extern void do_coredump(const kernel_siginfo_t *siginfo);
#else
static inline void do_coredump(const kernel_siginfo_t *siginfo) {}
Expand Down

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