Under certain circumstances initialization of `unsigned seq` and `struct inode *inode` passed into step_into() may be skipped. In particular, if the call to lookup_fast() in walk_component() returns NULL, and lookup_slow() returns a valid dentry, then the `seq` and `inode` will remain uninitialized until the call to step_into() (see [1] for more info). Right now step_into() does not use these uninitialized values, yet passing uninitialized values to functions is considered undefined behavior (see [2]). To fix that, we initialize `seq` and `inode` at definition. [1] https://github.com/ClangBuiltLinux/linux/issues/1648#issuecomment-1146608063 [2] https://lore.kernel.org/linux-toolchains/CAHk-=whjz3wO8zD+itoerphWem+JZz4uS3myf6u1Wd6epGRgmQ@xxxxxxxxxxxxxx/ Cc: Evgenii Stepanov <eugenis@xxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Marco Elver <elver@xxxxxxxxxx> Cc: Nathan Chancellor <nathan@xxxxxxxxxx> Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Vitaly Buka <vitalybuka@xxxxxxxxxx> Cc: linux-kernel@xxxxxxxxxxxxxxx Cc: linux-toolchains@xxxxxxxxxxxxxxx Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> --- Link: https://linux-review.googlesource.com/id/I94d4e8cc1f0ecc7174659e9506ce96aaf2201d0a --- fs/namei.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 1f28d3f463c3b..6b39dfd3b41bc 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1995,8 +1995,8 @@ static const char *handle_dots(struct nameidata *nd, int type) static const char *walk_component(struct nameidata *nd, int flags) { struct dentry *dentry; - struct inode *inode; - unsigned seq; + struct inode *inode = NULL; + unsigned seq = 0; /* * "." and ".." are special - ".." especially so because it has * to be able to know about the current root directory and @@ -3393,8 +3393,8 @@ static const char *open_last_lookups(struct nameidata *nd, struct dentry *dir = nd->path.dentry; int open_flag = op->open_flag; bool got_write = false; - unsigned seq; - struct inode *inode; + unsigned seq = 0; + struct inode *inode = NULL; struct dentry *dentry; const char *res; -- 2.37.0.rc0.161.g10f37bed90-goog
