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-rw-r--r--fs/exec.c49
1 files changed, 15 insertions, 34 deletions
diff --git a/fs/exec.c b/fs/exec.c
index 7ea097f6b341..f039386499db 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1614,43 +1614,24 @@ EXPORT_SYMBOL(set_binfmt);
/*
* set_dumpable converts traditional three-value dumpable to two flags and
- * stores them into mm->flags. It modifies lower two bits of mm->flags, but
- * these bits are not changed atomically. So get_dumpable can observe the
- * intermediate state. To avoid doing unexpected behavior, get get_dumpable
- * return either old dumpable or new one by paying attention to the order of
- * modifying the bits.
- *
- * dumpable | mm->flags (binary)
- * old new | initial interim final
- * ---------+-----------------------
- * 0 1 | 00 01 01
- * 0 2 | 00 10(*) 11
- * 1 0 | 01 00 00
- * 1 2 | 01 11 11
- * 2 0 | 11 10(*) 00
- * 2 1 | 11 11 01
- *
- * (*) get_dumpable regards interim value of 10 as 11.
+ * stores them into mm->flags.
*/
void set_dumpable(struct mm_struct *mm, int value)
{
- switch (value) {
- case SUID_DUMP_DISABLE:
- clear_bit(MMF_DUMPABLE, &mm->flags);
- smp_wmb();
- clear_bit(MMF_DUMP_SECURELY, &mm->flags);
- break;
- case SUID_DUMP_USER:
- set_bit(MMF_DUMPABLE, &mm->flags);
- smp_wmb();
- clear_bit(MMF_DUMP_SECURELY, &mm->flags);
- break;
- case SUID_DUMP_ROOT:
- set_bit(MMF_DUMP_SECURELY, &mm->flags);
- smp_wmb();
- set_bit(MMF_DUMPABLE, &mm->flags);
- break;
- }
+ unsigned long old, new;
+
+ 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);
+ }
+
+ } while (cmpxchg(&mm->flags, old, new) != old);
}
int __get_dumpable(unsigned long mm_flags)