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[PATCH] fix Data Acess error in dup_fd
author
Sharyathi Nagesh
<sharyath@in.ibm.com>
Fri, 10 Nov 2006 20:27:54 +0000
(12:27 -0800)
committer
Linus Torvalds
<torvalds@g5.osdl.org>
Mon, 13 Nov 2006 15:40:43 +0000
(07:40 -0800)
On running the Stress Test on machine for more than 72 hours following
error message was observed.
0:mon> e
cpu 0x0: Vector: 300 (Data Access) at [
c00000007ce2f7f0
]
pc:
c000000000060d90
: .dup_fd+0x240/0x39c
lr:
c000000000060d6c
: .dup_fd+0x21c/0x39c
sp:
c00000007ce2fa70
msr:
800000000000b032
dar:
ffffffff00000028
dsisr:
40000000
current = 0xc000000074950980
paca = 0xc000000000454500
pid = 27330, comm = bash
0:mon> t
[
c00000007ce2fa70
]
c000000000060d28
.dup_fd+0x1d8/0x39c (unreliable)
[
c00000007ce2fb30
]
c000000000060f48
.copy_files+0x5c/0x88
[
c00000007ce2fbd0
]
c000000000061f5c
.copy_process+0x574/0x1520
[
c00000007ce2fcd0
]
c000000000062f88
.do_fork+0x80/0x1c4
[
c00000007ce2fdc0
]
c000000000011790
.sys_clone+0x5c/0x74
[
c00000007ce2fe30
]
c000000000008950
.ppc_clone+0x8/0xc
The problem is because of race window. When if(expand) block is executed in
dup_fd unlocking of oldf->file_lock give a window for fdtable in oldf to be
modified. So actual open_files in oldf may not match with open_files
variable.
Cc: Vadim Lobanov <vlobanov@speakeasy.net>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
kernel/fork.c
patch
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diff --git
a/kernel/fork.c
b/kernel/fork.c
index 3da978eec791216dd796cd704aed67b263713fa1..4b4eab2a316136fc3bd44bdb7e55eeee509b1030 100644
(file)
--- a/
kernel/fork.c
+++ b/
kernel/fork.c
@@
-687,6
+687,7
@@
static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
* the latest pointer.
*/
spin_lock(&oldf->file_lock);
+ open_files = count_open_files(old_fdt);
old_fdt = files_fdtable(oldf);
}