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authorChandan Rajendra <chandan@linux.ibm.com>2019-01-22 12:21:52 +0530
committerAl Viro <viro@zeniv.linux.org.uk>2019-02-01 01:57:33 -0500
commitfbdb44013202305cd2aefb01df0a92bb55819702 (patch)
treed8e4924841ec469e9487eaac145eb8069efbe38b /fs/namespace.c
parent35ac1184244f1329783e1d897f74926d8bb1103a (diff)
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.c2
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;
}
/*