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authorTong Zhang <ztong0001@gmail.com>2022-01-30 00:40:55 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2022-01-30 10:56:58 +0300
commite7f1e8834b2b2144dfbe0b2235d05e4f6f95882e (patch)
tree86f8b9728b800bf46ac901916cffaa654fbb1a51
parent6cb917411e028dcb66ce8f5db1b47361b78d7d3f (diff)
downloadlinux-e7f1e8834b2b2144dfbe0b2235d05e4f6f95882e.tar.xz
binfmt_misc: fix crash when load/unload module
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. To reproduce: modprobe binfmt_misc modprobe -r binfmt_misc modprobe binfmt_misc modprobe -r binfmt_misc modprobe binfmt_misc resulting in modprobe: can't load module binfmt_misc (kernel/fs/binfmt_misc.ko): Cannot allocate memory and an unhappy kernel: binfmt_misc: Failed to create fs/binfmt_misc sysctl mount point binfmt_misc: Failed to create fs/binfmt_misc sysctl mount point BUG: unable to handle page fault for address: fffffbfff8004802 Call Trace: init_misc_binfmt+0x2d/0x1000 [binfmt_misc] Link: https://lkml.kernel.org/r/20220124181812.1869535-2-ztong0001@gmail.com Fixes: 3ba442d5331f ("fs: move binfmt_misc sysctl to its own file") Signed-off-by: Tong Zhang <ztong0001@gmail.com> Co-developed-by: Christian Brauner<brauner@kernel.org> Acked-by: Luis Chamberlain <mcgrof@kernel.org> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Kees Cook <keescook@chromium.org> Cc: Iurii Zaikin <yzaikin@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/binfmt_misc.c8
1 files 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);
}