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    Subject[BUG] nfs3_list_one_acl oops
    Today, I got a nice oops while trying to update my initramfs:

    Alignment trap: not handling instruction e1901f9f at [<c020b8ec>]
    Unhandled fault: alignment exception (0x001) at 0xffffffa1
    Internal error: : 1 [#1] SMP ARM
    Modules linked in: bnep rfcomm bluetooth nfsd exportfs hid_cypress brcmfmac brcmutil snd_soc_fsl_spdif imx_pcm_dma imx2_wdt imx_thermal imx_sdma snd_soc_imx_spdif
    CPU: 2 PID: 1704 Comm: cp Not tainted 3.16.0-rc6+ #1281
    task: e9be5580 ti: e3ce6000 task.ti: e3ce6000
    PC is at nfs3_list_one_acl+0x38/0xa0
    LR is at get_acl+0x4c/0x60
    pc : [<c020b8f0>] lr : [<c0144774>] psr: a00d0013
    sp : e3ce7f08 ip : e3ce7ee8 fp : e3ce7f2c
    r10: 00000000 r9 : e3ce6000 r8 : 00000000
    r7 : 00000000 r6 : c06d728c r5 : 00000000 r4 : e3ce7f3c
    r3 : 00000000 r2 : e3ce7ea4 r1 : 00003fe7 r0 : ffffffa1
    Flags: NzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
    Control: 10c5387d Table: 33dec04a DAC: 00000015
    Process cp (pid: 1704, stack limit = 0xe3ce6248)
    Stack: (0xe3ce7f08 to 0xe3ce8000)
    7f00: 00000000 e3ce7f3c 00000000 e9ff3858 00000000 00000000
    7f20: e3ce7f5c e3ce7f30 c020c0f8 c020b8c4 00000000 e3ce7f3c 00000000 00000000
    7f40: 00000000 c020c0b4 00000000 e8c05198 e3ce7f84 e3ce7f60 c011a0d0 c020c0c0
    7f60: e3d04600 e3d04600 00000000 00000000 c000ec04 00000000 e3ce7fa4 e3ce7f88
    7f80: c011aed8 c011a07c 00008000 be9995a8 b6f756db 000000ea 00000000 e3ce7fa8
    7fa0: c000ea80 c011aeb0 00008000 be9995a8 00000003 00000000 00000000 00022150
    7fc0: 00008000 be9995a8 b6f756db 000000ea be9994d8 b6f10d99 00000003 be9995a8
    7fe0: be9993a0 be999390 b6f105db b6ea8ca0 800d0010 00000003 6f74616c 69662d72
    Backtrace:
    [<c020b8b8>] (nfs3_list_one_acl) from [<c020c0f8>] (nfs3_listxattr+0x44/0x80)
    [<c020c0b4>] (nfs3_listxattr) from [<c011a0d0>] (listxattr+0x60/0x11c)
    [<c011a070>] (listxattr) from [<c011aed8>] (SyS_flistxattr+0x34/0x58)
    [<c011aea4>] (SyS_flistxattr) from [<c000ea80>] (ret_fast_syscall+0x0/0x30)
    Code: 0a000016 f57ff05b f590f000 e1901f9f (e2411001)
    ---[ end trace 05ecbdab16531f0b ]---

    The problem is that get_acl() does *not* return NULL on error, it returns
    an error code. Hence this:

    + acl = get_acl(inode, type);
    + if (!acl)
    + return 0;

    introduced by 74adf83f5d77 ("nfs: only show Posix ACLs in listxattr if
    actually present") ends up breaking when get_acl() fails (as is the case
    if NFS is used against a server with ACL support disabled.)

    The original commit was marked for stable, which means that this brokenness
    is going to spread to all stable kernels.

    Fixes: 74adf83f5d77 ("nfs: only show Posix ACLs in listxattr if actually present")
    Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
    Cc: <stable@vger.kernel.org>
    Cc: Trond Myklebust <trond.myklebust@primarydata.com>
    ---

    I've included <stable@vger.kernel.org> in the Cc list so they can hold off
    spreading the broken patch further into stable trees until this issue is
    resolved.

    fs/nfs/nfs3acl.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/fs/nfs/nfs3acl.c b/fs/nfs/nfs3acl.c
    index 8f854dde4150..ada8c66aa9e5 100644
    --- a/fs/nfs/nfs3acl.c
    +++ b/fs/nfs/nfs3acl.c
    @@ -256,7 +256,7 @@ nfs3_list_one_acl(struct inode *inode, int type, const char *name, void *data,
    char *p = data + *result;

    acl = get_acl(inode, type);
    - if (!acl)
    + if (IS_ERR(acl))
    return 0;

    posix_acl_release(acl);

    --
    FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up
    according to speedtest.net.


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