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Message-ID: <20070731070538.GD2412@kernel.sg>
Date: Tue, 31 Jul 2007 15:05:38 +0800
From: Eugene Teo <eugeneteo@...nel.sg>
To: linux-kernel@...r.kernel.org
Cc: "Kawai, Hidehiro" <hidehiro.kawai.ez@...achi.com>,
Neil Horman <nhorman@...driver.com>,
Bryan Wu <bryan.wu@...log.com>
Subject: [PATCH 3/3] coredump: re-implement suid_dumpable using a flag
Hidehiro-san re-implemented suid_dumpable using a pair of bit flags. But
since we no longer permitting users to call prctl(PR_SET_DUMPABLE, 2),
there is no need to waste a bit of mm_struct.flags for something that will
never be used.
Signed-off-by: Eugene Teo <eugeneteo@...nel.sg>
---
fs/exec.c | 42 +++++-------------------------------------
include/linux/sched.h | 13 ++++++-------
2 files changed, 11 insertions(+), 44 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index 60b4080..0f30b94 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1666,53 +1666,21 @@ fail:
}
/*
- * 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.
+ * set_dumpable converts traditional two-value dumpable to one flag and
+ * stores it in mm->flags. It modifies the lower bit of mm->flags.
*/
void set_dumpable(struct mm_struct *mm, int value)
{
- switch (value) {
- case 0:
+ if (value == 0)
clear_bit(MMF_DUMPABLE, &mm->flags);
- smp_wmb();
- clear_bit(MMF_DUMP_SECURELY, &mm->flags);
- break;
- case 1:
- set_bit(MMF_DUMPABLE, &mm->flags);
- smp_wmb();
- clear_bit(MMF_DUMP_SECURELY, &mm->flags);
- break;
- case 2:
- set_bit(MMF_DUMP_SECURELY, &mm->flags);
- smp_wmb();
+ else if (value == 1)
set_bit(MMF_DUMPABLE, &mm->flags);
- break;
- }
}
EXPORT_SYMBOL_GPL(set_dumpable);
int get_dumpable(struct mm_struct *mm)
{
- int ret;
-
- ret = mm->flags & 0x3;
- return (ret >= 2) ? 2 : ret;
+ return (mm->flags & 0x1);
}
int do_coredump(long signr, int exit_code, struct pt_regs * regs)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2e49027..8a0092d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -350,15 +350,14 @@ extern int get_dumpable(struct mm_struct *mm);
/* mm flags */
/* dumpable bits */
-#define MMF_DUMPABLE 0 /* core dump is permitted */
-#define MMF_DUMP_SECURELY 1 /* core file is readable only by root */
-#define MMF_DUMPABLE_BITS 2
+#define MMF_DUMPABLE 0 /* core dump is permitted */
+#define MMF_DUMPABLE_BITS 1
/* coredump filter bits */
-#define MMF_DUMP_ANON_PRIVATE 2
-#define MMF_DUMP_ANON_SHARED 3
-#define MMF_DUMP_MAPPED_PRIVATE 4
-#define MMF_DUMP_MAPPED_SHARED 5
+#define MMF_DUMP_ANON_PRIVATE 1
+#define MMF_DUMP_ANON_SHARED 2
+#define MMF_DUMP_MAPPED_PRIVATE 3
+#define MMF_DUMP_MAPPED_SHARED 4
#define MMF_DUMP_FILTER_SHIFT MMF_DUMPABLE_BITS
#define MMF_DUMP_FILTER_BITS 4
#define MMF_DUMP_FILTER_MASK \
-
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