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Commit 7288e118 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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coredump: kill MMF_DUMPABLE and MMF_DUMP_SECURELY 



Nobody actually needs MMF_DUMPABLE/MMF_DUMP_SECURELY, they are only used
to enforce the encoding of SUID_DUMP_* enum in mm->flags &
MMF_DUMPABLE_MASK.

Now that set_dumpable() updates both bits atomically we can kill them and
simply store the value "as is" in 2 lower bits.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Cc: Alex Kelly <alex.page.kelly@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Petr Matousek <pmatouse@redhat.com>
Cc: Vasily Kulikov <segoon@openwall.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent abacd2fe

fs/exec.c

+6 −15
Original line number Diff line number Diff line
@@ -1613,33 +1613,24 @@ void set_binfmt(struct linux_binfmt *new) 
EXPORT_SYMBOL(set_binfmt);



/*

 * set_dumpable converts traditional three-value dumpable to two flags and

 * stores them into mm->flags.

 * set_dumpable stores three-value SUID_DUMP_* into mm->flags.

 */

void set_dumpable(struct mm_struct *mm, int value)

{

	unsigned long old, new;



	if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))

		return;



	do {

		old = ACCESS_ONCE(mm->flags);

		new = old & ~MMF_DUMPABLE_MASK;



		switch (value) {

		case SUID_DUMP_ROOT:

			new |= (1 << MMF_DUMP_SECURELY);

		case SUID_DUMP_USER:

			new |= (1<< MMF_DUMPABLE);

		}



		new = (old & ~MMF_DUMPABLE_MASK) | value;

	} while (cmpxchg(&mm->flags, old, new) != old);

}



int __get_dumpable(unsigned long mm_flags)

{

	int ret;



	ret = mm_flags & MMF_DUMPABLE_MASK;

	return (ret > SUID_DUMP_USER) ? SUID_DUMP_ROOT : ret;

	return mm_flags & MMF_DUMPABLE_MASK;

}



/*

include/linux/sched.h

+1 −3
Original line number Diff line number Diff line
@@ -400,10 +400,8 @@ extern int get_dumpable(struct mm_struct *mm); 
#define SUID_DUMP_ROOT		2	/* Dump as root */



/* mm flags */

/* dumpable bits */

#define MMF_DUMPABLE      0  /* core dump is permitted */

#define MMF_DUMP_SECURELY 1  /* core file is readable only by root */



/* for SUID_DUMP_* above */

#define MMF_DUMPABLE_BITS 2

#define MMF_DUMPABLE_MASK ((1 << MMF_DUMPABLE_BITS) - 1)