Re: Linux 2.4.30-rc2 - fix for CAN-2005-0794: Potential DOS in load_elf_library
On Sat, Mar 26, 2005 at 01:14:01PM +0100, Andreas Arens wrote: > Hi Marcelo, Herbert, > > I'm just reading the patch so don't know of any hidden side-effects which > might cure it, but this clearly looks like a possibly deadlocking typo in > fs/binfmt_elf.c to me: > > > >- while (elf_phdata->p_type != PT_LOAD) elf_phdata++; > >+ while (elf_phdata->p_type != PT_LOAD) > >+ eppnt++; > > Shouldn't this be: > > - while (elf_phdata->p_type != PT_LOAD) elf_phdata++; > + while (eppnt->p_type != PT_LOAD) > + eppnt++; Doh. Yes, it is. I change it accordingly, will release another -rc :( - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: Potential DOS in load_elf_library?
On Fri, Mar 18, 2005 at 01:05:01AM -0800, Andrew Morton wrote:
>
> I think it'd be better to use epptr everywhere, so we can see that it only
> gets assigned, tested then freed.
Looks good to me.
Cheers,
--
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Email: Herbert Xu ~{PmV>HI~} <[EMAIL PROTECTED]>
Home Page: http://gondor.apana.org.au/~herbert/
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-
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Re: Potential DOS in load_elf_library?
Herbert Xu <[EMAIL PROTECTED]> wrote:
>
> Yichen Xie <[EMAIL PROTECTED]> wrote:
> > Hi guys, I was looking at the load_elf_library function (fs/binfmt_elf.c)
> > in 2.6.10, and noticed the following:
> >
> >elf_phdata = (struct elf_phdr *) kmalloc(j, GFP_KERNEL);
> >...
> >while (elf_phdata->p_type != PT_LOAD) elf_phdata++;
> >...
> >kfree(elf_phdata);
> >
> > Could this be problematic since the pointer being freed might be different
> > from that returned from kmalloc?
>
> Indeed. This bug has been around since last century.
Duh, I was looking at the wrong function. Thanks.
> How does this look?
I think it'd be better to use epptr everywhere, so we can see that it only
gets assigned, tested then freed.
--- 25/fs/binfmt_elf.c~load_elf_binary-kfree-fix2005-03-18
01:00:49.0 -0800
+++ 25-akpm/fs/binfmt_elf.c 2005-03-18 01:03:14.0 -0800
@@ -1028,6 +1028,7 @@ out_free_ph:
static int load_elf_library(struct file *file)
{
struct elf_phdr *elf_phdata;
+ struct elf_phdr *eppnt;
unsigned long elf_bss, bss, len;
int retval, error, i, j;
struct elfhdr elf_ex;
@@ -1051,44 +1052,47 @@ static int load_elf_library(struct file
/* j < ELF_MIN_ALIGN because elf_ex.e_phnum <= 2 */
error = -ENOMEM;
- elf_phdata = (struct elf_phdr *) kmalloc(j, GFP_KERNEL);
+ elf_phdata = kmalloc(j, GFP_KERNEL);
if (!elf_phdata)
goto out;
+ eppnt = elf_phdata;
error = -ENOEXEC;
- retval = kernel_read(file, elf_ex.e_phoff, (char *) elf_phdata, j);
+ retval = kernel_read(file, elf_ex.e_phoff, (char *)eppnt, j);
if (retval != j)
goto out_free_ph;
for (j = 0, i = 0; ip_type == PT_LOAD) j++;
+ if ((eppnt + i)->p_type == PT_LOAD)
+ j++;
if (j != 1)
goto out_free_ph;
- while (elf_phdata->p_type != PT_LOAD) elf_phdata++;
+ while (eppnt->p_type != PT_LOAD)
+ eppnt++;
/* Now use mmap to map the library into memory. */
down_write(¤t->mm->mmap_sem);
error = do_mmap(file,
- ELF_PAGESTART(elf_phdata->p_vaddr),
- (elf_phdata->p_filesz +
-ELF_PAGEOFFSET(elf_phdata->p_vaddr)),
+ ELF_PAGESTART(eppnt->p_vaddr),
+ (eppnt->p_filesz +
+ELF_PAGEOFFSET(eppnt->p_vaddr)),
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
- (elf_phdata->p_offset -
-ELF_PAGEOFFSET(elf_phdata->p_vaddr)));
+ (eppnt->p_offset -
+ELF_PAGEOFFSET(eppnt->p_vaddr)));
up_write(¤t->mm->mmap_sem);
- if (error != ELF_PAGESTART(elf_phdata->p_vaddr))
+ if (error != ELF_PAGESTART(eppnt->p_vaddr))
goto out_free_ph;
- elf_bss = elf_phdata->p_vaddr + elf_phdata->p_filesz;
+ elf_bss = eppnt->p_vaddr + eppnt->p_filesz;
if (padzero(elf_bss)) {
error = -EFAULT;
goto out_free_ph;
}
- len = ELF_PAGESTART(elf_phdata->p_filesz + elf_phdata->p_vaddr +
ELF_MIN_ALIGN - 1);
- bss = elf_phdata->p_memsz + elf_phdata->p_vaddr;
+ len = ELF_PAGESTART(eppnt->p_filesz + eppnt->p_vaddr + ELF_MIN_ALIGN -
1);
+ bss = eppnt->p_memsz + eppnt->p_vaddr;
if (bss > len) {
down_write(¤t->mm->mmap_sem);
do_brk(len, bss - len);
_
-
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Re: Potential DOS in load_elf_library?
Yichen Xie <[EMAIL PROTECTED]> wrote:
> Hi guys, I was looking at the load_elf_library function (fs/binfmt_elf.c)
> in 2.6.10, and noticed the following:
>
>elf_phdata = (struct elf_phdr *) kmalloc(j, GFP_KERNEL);
>...
>while (elf_phdata->p_type != PT_LOAD) elf_phdata++;
>...
>kfree(elf_phdata);
>
> Could this be problematic since the pointer being freed might be different
> from that returned from kmalloc?
Indeed. This bug has been around since last century. How does this
look?
Cheers,
--
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <[EMAIL PROTECTED]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
--
= fs/binfmt_elf.c 1.106 vs edited =
--- 1.106/fs/binfmt_elf.c 2005-03-14 10:29:43 +11:00
+++ edited/fs/binfmt_elf.c 2005-03-18 19:46:37 +11:00
@@ -1026,6 +1026,7 @@
static int load_elf_library(struct file *file)
{
struct elf_phdr *elf_phdata;
+ struct elf_phdr *eppnt;
unsigned long elf_bss, bss, len;
int retval, error, i, j;
struct elfhdr elf_ex;
@@ -1063,30 +1064,32 @@
if (j != 1)
goto out_free_ph;
- while (elf_phdata->p_type != PT_LOAD) elf_phdata++;
+ eppnt = elf_phdata;
+ while (eppnt->p_type != PT_LOAD)
+ eppnt++;
/* Now use mmap to map the library into memory. */
down_write(¤t->mm->mmap_sem);
error = do_mmap(file,
- ELF_PAGESTART(elf_phdata->p_vaddr),
- (elf_phdata->p_filesz +
-ELF_PAGEOFFSET(elf_phdata->p_vaddr)),
+ ELF_PAGESTART(eppnt->p_vaddr),
+ (eppnt->p_filesz +
+ELF_PAGEOFFSET(eppnt->p_vaddr)),
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
- (elf_phdata->p_offset -
-ELF_PAGEOFFSET(elf_phdata->p_vaddr)));
+ (eppnt->p_offset -
+ELF_PAGEOFFSET(eppnt->p_vaddr)));
up_write(¤t->mm->mmap_sem);
- if (error != ELF_PAGESTART(elf_phdata->p_vaddr))
+ if (error != ELF_PAGESTART(eppnt->p_vaddr))
goto out_free_ph;
- elf_bss = elf_phdata->p_vaddr + elf_phdata->p_filesz;
+ elf_bss = eppnt->p_vaddr + eppnt->p_filesz;
if (padzero(elf_bss)) {
error = -EFAULT;
goto out_free_ph;
}
- len = ELF_PAGESTART(elf_phdata->p_filesz + elf_phdata->p_vaddr +
ELF_MIN_ALIGN - 1);
- bss = elf_phdata->p_memsz + elf_phdata->p_vaddr;
+ len = ELF_PAGESTART(eppnt->p_filesz + eppnt->p_vaddr + ELF_MIN_ALIGN -
1);
+ bss = eppnt->p_memsz + eppnt->p_vaddr;
if (bss > len) {
down_write(¤t->mm->mmap_sem);
do_brk(len, bss - len);
-
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Re: Potential DOS in load_elf_library?
Yichen Xie <[EMAIL PROTECTED]> wrote: > > Hi guys, I was looking at the load_elf_library function (fs/binfmt_elf.c) > in 2.6.10, and noticed the following: > > elf_phdata = (struct elf_phdr *) kmalloc(j, GFP_KERNEL); > ... > while (elf_phdata->p_type != PT_LOAD) elf_phdata++; > ... > kfree(elf_phdata); > > Could this be problematic since the pointer being freed might be different > from that returned from kmalloc? Current kernels seem to be OK. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Potential DOS in load_elf_library?
Hi guys, I was looking at the load_elf_library function (fs/binfmt_elf.c) in 2.6.10, and noticed the following: elf_phdata = (struct elf_phdr *) kmalloc(j, GFP_KERNEL); ... while (elf_phdata->p_type != PT_LOAD) elf_phdata++; ... kfree(elf_phdata); Could this be problematic since the pointer being freed might be different from that returned from kmalloc? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
