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| author |   Chandan Rajendra <chandan@linux.ibm.com> | 2019-01-22 12:21:52 +0530 |
|---|---|---|
| committer |   Al Viro <viro@zeniv.linux.org.uk> | 2019-02-01 01:57:33 -0500 |
| commit | fbdb44013202305cd2aefb01df0a92bb55819702 (patch) | |
| tree | d8e4924841ec469e9487eaac145eb8069efbe38b /fs/namespace.c | |
| parent | cgroup: saner refcounting for cgroup_root (diff) | |
| download | linux-dev-fbdb44013202305cd2aefb01df0a92bb55819702.tar.xz linux-dev-fbdb44013202305cd2aefb01df0a92bb55819702.zip | |
copy_mount_string: Limit string length to PATH_MAX
On ppc64le, When a string with PAGE_SIZE - 1 (i.e. 64k-1) length is
passed as a "filesystem type" argument to the mount(2) syscall,
copy_mount_string() ends up allocating 64k (the PAGE_SIZE on ppc64le)
worth of space for holding the string in kernel's address space.
Later, in set_precision() (invoked by get_fs_type() ->
__request_module() -> vsnprintf()), we end up assigning
strlen(fs-type-string) i.e. 65535 as the
value to 'struct printf_spec'->precision member. This field has a width
of 16 bits and it is a signed data type. Hence an invalid value ends
up getting assigned. This causes the "WARN_ONCE(spec->precision != prec,
"precision %d too large", prec)" statement inside set_precision() to be
executed.
This commit fixes the bug by limiting the length of the string passed by
copy_mount_string() to strndup_user() to PATH_MAX.
Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com>
Reported-by: Abdul Haleem <abdhalee@linux.ibm.com>
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index a677b59efd74..c373c769e0ce 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2746,7 +2746,7 @@ void *copy_mount_options(const void __user * data) char *copy_mount_string(const void __user *data) { - return data ? strndup_user(data, PAGE_SIZE) : NULL; + return data ? strndup_user(data, PATH_MAX) : NULL; } /* |