[PATCH 4.4 018/118] kexec: fix double-free when failing to relocate the purgatory

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

--

From: Thiago Jung Bauermann 

commit 070c43eea5043e950daa423707ae3c77e2f48edb upstream.

If kexec_apply_relocations fails, kexec_load_purgatory frees pi->sechdrs
and pi->purgatory_buf.  This is redundant, because in case of error
kimage_file_prepare_segments calls kimage_file_post_load_cleanup, which
will also free those buffers.

This causes two warnings like the following, one for pi->sechdrs and the
other for pi->purgatory_buf:

  kexec-bzImage64: Loading purgatory failed
  [ cut here ]
  WARNING: CPU: 1 PID: 2119 at mm/vmalloc.c:1490 __vunmap+0xc1/0xd0
  Trying to vfree() nonexistent vm area (c9e91000)
  Modules linked in:
  CPU: 1 PID: 2119 Comm: kexec Not tainted 4.8.0-rc3+ #5
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  Call Trace:
dump_stack+0x4d/0x65
__warn+0xcb/0xf0
warn_slowpath_fmt+0x4f/0x60
? find_vmap_area+0x19/0x70
? kimage_file_post_load_cleanup+0x47/0xb0
__vunmap+0xc1/0xd0
vfree+0x2e/0x70
kimage_file_post_load_cleanup+0x5e/0xb0
SyS_kexec_file_load+0x448/0x680
? putname+0x54/0x60
? do_sys_open+0x190/0x1f0
entry_SYSCALL_64_fastpath+0x13/0x8f
  ---[ end trace 158bb74f5950ca2b ]---

Fix by setting pi->sechdrs an pi->purgatory_buf to NULL, since vfree
won't try to free a NULL pointer.

Link: 
http://lkml.kernel.org/r/1472083546-23683-1-git-send-email-bauer...@linux.vnet.ibm.com
Signed-off-by: Thiago Jung Bauermann 
Acked-by: Baoquan He 
Cc: "Eric W. Biederman" 
Cc: Vivek Goyal 
Cc: Dave Young 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman 

---
 kernel/kexec_file.c |3 +++
 1 file changed, 3 insertions(+)

--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -934,7 +934,10 @@ int kexec_load_purgatory(struct kimage *
return 0;
 out:
vfree(pi->sechdrs);
+   pi->sechdrs = NULL;
+
vfree(pi->purgatory_buf);
+   pi->purgatory_buf = NULL;
return ret;
 }
 

[PATCH 4.4 018/118] kexec: fix double-free when failing to relocate the purgatory

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

--

From: Thiago Jung Bauermann 

commit 070c43eea5043e950daa423707ae3c77e2f48edb upstream.

If kexec_apply_relocations fails, kexec_load_purgatory frees pi->sechdrs
and pi->purgatory_buf.  This is redundant, because in case of error
kimage_file_prepare_segments calls kimage_file_post_load_cleanup, which
will also free those buffers.

This causes two warnings like the following, one for pi->sechdrs and the
other for pi->purgatory_buf:

  kexec-bzImage64: Loading purgatory failed
  [ cut here ]
  WARNING: CPU: 1 PID: 2119 at mm/vmalloc.c:1490 __vunmap+0xc1/0xd0
  Trying to vfree() nonexistent vm area (c9e91000)
  Modules linked in:
  CPU: 1 PID: 2119 Comm: kexec Not tainted 4.8.0-rc3+ #5
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  Call Trace:
dump_stack+0x4d/0x65
__warn+0xcb/0xf0
warn_slowpath_fmt+0x4f/0x60
? find_vmap_area+0x19/0x70
? kimage_file_post_load_cleanup+0x47/0xb0
__vunmap+0xc1/0xd0
vfree+0x2e/0x70
kimage_file_post_load_cleanup+0x5e/0xb0
SyS_kexec_file_load+0x448/0x680
? putname+0x54/0x60
? do_sys_open+0x190/0x1f0
entry_SYSCALL_64_fastpath+0x13/0x8f
  ---[ end trace 158bb74f5950ca2b ]---

Fix by setting pi->sechdrs an pi->purgatory_buf to NULL, since vfree
won't try to free a NULL pointer.

Link: 
http://lkml.kernel.org/r/1472083546-23683-1-git-send-email-bauer...@linux.vnet.ibm.com
Signed-off-by: Thiago Jung Bauermann 
Acked-by: Baoquan He 
Cc: "Eric W. Biederman" 
Cc: Vivek Goyal 
Cc: Dave Young 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman 

---
 kernel/kexec_file.c |3 +++
 1 file changed, 3 insertions(+)

--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -934,7 +934,10 @@ int kexec_load_purgatory(struct kimage *
return 0;
 out:
vfree(pi->sechdrs);
+   pi->sechdrs = NULL;
+
vfree(pi->purgatory_buf);
+   pi->purgatory_buf = NULL;
return ret;
 }