lkml.org 
[lkml]   [2022]   [Jan]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v2 1/2] binfmt_misc: fix crash when load/unload module
    Date
    We should unregister the table upon module unload otherwise something
    horrible will happen when we load binfmt_misc module again. Also note
    that we should keep value returned by register_sysctl_mount_point() and
    release it later, otherwise it will leak.
    Also, per Christian's comment, to fully restore the old behavior that
    won't break userspace the check(binfmt_misc_header) should be
    eliminated.

    reproduce:
    modprobe binfmt_misc
    modprobe -r binfmt_misc
    modprobe binfmt_misc
    modprobe -r binfmt_misc
    modprobe binfmt_misc

    [ 18.032038] Call Trace:
    [ 18.032108] <TASK>
    [ 18.032169] dump_stack_lvl+0x34/0x44
    [ 18.032273] __register_sysctl_table+0x6f4/0x720
    [ 18.032397] ? preempt_count_sub+0xf/0xb0
    [ 18.032508] ? 0xffffffffc0040000
    [ 18.032600] init_misc_binfmt+0x2d/0x1000 [binfmt_misc]
    [ 18.042520] binfmt_misc: Failed to create fs/binfmt_misc sysctl mount point
    modprobe: can't load module binfmt_misc (kernel/fs/binfmt_misc.ko): Cannot allocate memory
    [ 18.063549] binfmt_misc: Failed to create fs/binfmt_misc sysctl mount point
    [ 18.204779] BUG: unable to handle page fault for address: fffffbfff8004802

    Fixes: 3ba442d5331f ("fs: move binfmt_misc sysctl to its own file")
    Co-developed-by: Christian Brauner<brauner@kernel.org>
    Signed-off-by: Tong Zhang <ztong0001@gmail.com>
    ---
    fs/binfmt_misc.c | 8 ++++----
    1 file changed, 4 insertions(+), 4 deletions(-)

    diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
    index ddea6acbddde..c07f35719ee3 100644
    --- a/fs/binfmt_misc.c
    +++ b/fs/binfmt_misc.c
    @@ -817,20 +817,20 @@ static struct file_system_type bm_fs_type = {
    };
    MODULE_ALIAS_FS("binfmt_misc");

    +static struct ctl_table_header *binfmt_misc_header;
    +
    static int __init init_misc_binfmt(void)
    {
    int err = register_filesystem(&bm_fs_type);
    if (!err)
    insert_binfmt(&misc_format);
    - if (!register_sysctl_mount_point("fs/binfmt_misc")) {
    - pr_warn("Failed to create fs/binfmt_misc sysctl mount point");
    - return -ENOMEM;
    - }
    + binfmt_misc_header = register_sysctl_mount_point("fs/binfmt_misc");
    return 0;
    }

    static void __exit exit_misc_binfmt(void)
    {
    + unregister_sysctl_table(binfmt_misc_header);
    unregister_binfmt(&misc_format);
    unregister_filesystem(&bm_fs_type);
    }
    --
    2.25.1
    \
     
     \ /
      Last update: 2022-01-24 19:20    [W:4.729 / U:0.036 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site