[PATCH] fix Data Acess error in dup_fd
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>