| Submitter | Julien Tinnes |
|---|---|
| Date | 2009-06-26 18:27:40 |
| Message ID | <deb7a2310906261127v2fd1564elb823716ae03fc0d4@mail.gmail.com> |
| Download | mbox | patch |
| Permalink | /patch/32598/ |
| State | New |
| Headers | show |
Comments
On Fri, Jun 26, 2009 at 08:27:40PM +0200, Julien Tinnes wrote: > Hello, > > We have found that the current PER_CLEAR_ON_SETID mask on Linux > doesn't include neither ADDR_COMPAT_LAYOUT, nor MMAP_PAGE_ZERO. > > The current mask is READ_IMPLIES_EXEC|ADDR_NO_RANDOMIZE. > > We believe it is important to add MMAP_PAGE_ZERO, because by using > this personality it is possible to have the first page mapped inside a > process running as setuid root. This could be used in those scenarios: I agree. > Less importantly, we believe ADDR_COMPAT_LAYOUT should also be added > since on x86 32bits it will in practice disable most of the address > space layout randomization (only the stack will remain randomized). Agree on this on, too. > -#define PER_CLEAR_ON_SETID (READ_IMPLIES_EXEC|ADDR_NO_RANDOMIZE) > +#define PER_CLEAR_ON_SETID > (READ_IMPLIES_EXEC|ADDR_NO_RANDOMIZE|ADDR_COMPAT_LAYOUT|MMAP_PAGE_ZERO) #define PER_CLEAR_ON_SETID \ (READ_IMPLIES_EXEC | \ ADDR_NO_RANDOMIZE | \ ADDR_COMPAT_LAYOUT | \ MMAP_PAGE_ZERO) to make it a little more readable (and work around your mailer corrupting long lines :)) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Patch
diff -r f70f443c9ead include/linux/personality.h --- a/include/linux/personality.h Fri Jun 26 19:59:33 2009 +0200 +++ b/include/linux/personality.h Fri Jun 26 20:00:40 2009 +0200 @@ -40,7 +40,7 @@ enum { * Security-relevant compatibility flags that must be * cleared upon setuid or setgid exec: */ -#define PER_CLEAR_ON_SETID (READ_IMPLIES_EXEC|ADDR_NO_RANDOMIZE) +#define PER_CLEAR_ON_SETID (READ_IMPLIES_EXEC|ADDR_NO_RANDOMIZE|ADDR_COMPAT_LAYOUT|MMAP_PAGE_ZERO) /*
Hello, We have found that the current PER_CLEAR_ON_SETID mask on Linux doesn't include neither ADDR_COMPAT_LAYOUT, nor MMAP_PAGE_ZERO. The current mask is READ_IMPLIES_EXEC|ADDR_NO_RANDOMIZE. We believe it is important to add MMAP_PAGE_ZERO, because by using this personality it is possible to have the first page mapped inside a process running as setuid root. This could be used in those scenarios: - Exploiting a NULL pointer dereference issue in a setuid root binary - Bypassing the mmap_min_addr restrictions of the Linux kernel: by running a setuid binary that would drop privileges before giving us control back (for instance by loading a user-supplied library), we could get the first page mapped in a process we control. By further using mremap and mprotect on this mapping, we can then completely bypass the mmap_min_addr restrictions. Less importantly, we believe ADDR_COMPAT_LAYOUT should also be added since on x86 32bits it will in practice disable most of the address space layout randomization (only the stack will remain randomized). Signed-off-by: Julien Tinnes <jt@cr0.org> and Tavis Ormandy <taviso@sdf.lonestar.org> --- * Personality types. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/