| Message ID | 20220127152720.25898-1-mathieu.desnoyers@efficios.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | bfdf4e6208051ed7165b2e92035b4bf11f43eb63 |
| Headers | show |
| Series | [RFC,v2] rseq: Remove broken uapi field layout on 32-bit little endian | expand |
On Thu, Jan 27, 2022 at 10:27:20AM -0500, Mathieu Desnoyers wrote: > The rseq rseq_cs.ptr.{ptr32,padding} uapi endianness handling is > entirely wrong on 32-bit little endian: a preprocessor logic mistake > wrongly uses the big endian field layout on 32-bit little endian > architectures. > > Fortunately, those ptr32 accessors were never used within the kernel, > and only meant as a convenience for user-space. > > Remove those and replace the whole rseq_cs union by a __u64 type, as > this is the only thing really needed to express the ABI. Document how > 32-bit architectures are meant to interact with this field. > > Fixes: ec9c82e03a74 ("rseq: uapi: Declare rseq_cs field as union, update includes") > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> > Cc: Florian Weimer <fw@deneb.enyo.de> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: linux-api@vger.kernel.org > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Boqun Feng <boqun.feng@gmail.com> > Cc: Andy Lutomirski <luto@amacapital.net> > Cc: Dave Watson <davejwatson@fb.com> > Cc: Paul Turner <pjt@google.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Russell King <linux@arm.linux.org.uk> > Cc: "H . Peter Anvin" <hpa@zytor.com> > Cc: Andi Kleen <andi@firstfloor.org> > Cc: Christian Brauner <christian.brauner@ubuntu.com> > Cc: Ben Maurer <bmaurer@fb.com> > Cc: Steven Rostedt <rostedt@goodmis.org> > Cc: Josh Triplett <josh@joshtriplett.org> > Cc: Linus Torvalds <torvalds@linux-foundation.org> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Michael Kerrisk <mtk.manpages@gmail.com> > Cc: Joel Fernandes <joelaf@google.com> > Cc: Paul E. McKenney <paulmck@kernel.org> > --- Looks way cleaner now! Fwiw, Acked-by: Christian Brauner <brauner@kernel.org> > include/uapi/linux/rseq.h | 20 ++++---------------- > kernel/rseq.c | 8 ++++---- > 2 files changed, 8 insertions(+), 20 deletions(-) > > diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h > index 9a402fdb60e9..77ee207623a9 100644 > --- a/include/uapi/linux/rseq.h > +++ b/include/uapi/linux/rseq.h > @@ -105,23 +105,11 @@ struct rseq { > * Read and set by the kernel. Set by user-space with single-copy > * atomicity semantics. This field should only be updated by the > * thread which registered this data structure. Aligned on 64-bit. > + * > + * 32-bit architectures should update the low order bits of the > + * rseq_cs field, leaving the high order bits initialized to 0. > */ > - union { > - __u64 ptr64; > -#ifdef __LP64__ > - __u64 ptr; > -#else > - struct { > -#if (defined(__BYTE_ORDER) && (__BYTE_ORDER == __BIG_ENDIAN)) || defined(__BIG_ENDIAN) > - __u32 padding; /* Initialized to zero. */ > - __u32 ptr32; > -#else /* LITTLE */ > - __u32 ptr32; > - __u32 padding; /* Initialized to zero. */ > -#endif /* ENDIAN */ > - } ptr; > -#endif > - } rseq_cs; > + __u64 rseq_cs; > > /* > * Restartable sequences flags field. > diff --git a/kernel/rseq.c b/kernel/rseq.c > index 6d45ac3dae7f..97ac20b4f738 100644 > --- a/kernel/rseq.c > +++ b/kernel/rseq.c > @@ -128,10 +128,10 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) > int ret; > > #ifdef CONFIG_64BIT > - if (get_user(ptr, &t->rseq->rseq_cs.ptr64)) > + if (get_user(ptr, &t->rseq->rseq_cs)) > return -EFAULT; > #else > - if (copy_from_user(&ptr, &t->rseq->rseq_cs.ptr64, sizeof(ptr))) > + if (copy_from_user(&ptr, &t->rseq->rseq_cs, sizeof(ptr))) > return -EFAULT; > #endif > if (!ptr) { > @@ -217,9 +217,9 @@ static int clear_rseq_cs(struct task_struct *t) > * Set rseq_cs to NULL. > */ > #ifdef CONFIG_64BIT > - return put_user(0UL, &t->rseq->rseq_cs.ptr64); > + return put_user(0UL, &t->rseq->rseq_cs); > #else > - if (clear_user(&t->rseq->rseq_cs.ptr64, sizeof(t->rseq->rseq_cs.ptr64))) > + if (clear_user(&t->rseq->rseq_cs, sizeof(t->rseq->rseq_cs))) > return -EFAULT; > return 0; > #endif > -- > 2.17.1 >
diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h index 9a402fdb60e9..77ee207623a9 100644 --- a/include/uapi/linux/rseq.h +++ b/include/uapi/linux/rseq.h @@ -105,23 +105,11 @@ struct rseq { * Read and set by the kernel. Set by user-space with single-copy * atomicity semantics. This field should only be updated by the * thread which registered this data structure. Aligned on 64-bit. + * + * 32-bit architectures should update the low order bits of the + * rseq_cs field, leaving the high order bits initialized to 0. */ - union { - __u64 ptr64; -#ifdef __LP64__ - __u64 ptr; -#else - struct { -#if (defined(__BYTE_ORDER) && (__BYTE_ORDER == __BIG_ENDIAN)) || defined(__BIG_ENDIAN) - __u32 padding; /* Initialized to zero. */ - __u32 ptr32; -#else /* LITTLE */ - __u32 ptr32; - __u32 padding; /* Initialized to zero. */ -#endif /* ENDIAN */ - } ptr; -#endif - } rseq_cs; + __u64 rseq_cs; /* * Restartable sequences flags field. diff --git a/kernel/rseq.c b/kernel/rseq.c index 6d45ac3dae7f..97ac20b4f738 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -128,10 +128,10 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) int ret; #ifdef CONFIG_64BIT - if (get_user(ptr, &t->rseq->rseq_cs.ptr64)) + if (get_user(ptr, &t->rseq->rseq_cs)) return -EFAULT; #else - if (copy_from_user(&ptr, &t->rseq->rseq_cs.ptr64, sizeof(ptr))) + if (copy_from_user(&ptr, &t->rseq->rseq_cs, sizeof(ptr))) return -EFAULT; #endif if (!ptr) { @@ -217,9 +217,9 @@ static int clear_rseq_cs(struct task_struct *t) * Set rseq_cs to NULL. */ #ifdef CONFIG_64BIT - return put_user(0UL, &t->rseq->rseq_cs.ptr64); + return put_user(0UL, &t->rseq->rseq_cs); #else - if (clear_user(&t->rseq->rseq_cs.ptr64, sizeof(t->rseq->rseq_cs.ptr64))) + if (clear_user(&t->rseq->rseq_cs, sizeof(t->rseq->rseq_cs))) return -EFAULT; return 0; #endif
The rseq rseq_cs.ptr.{ptr32,padding} uapi endianness handling is entirely wrong on 32-bit little endian: a preprocessor logic mistake wrongly uses the big endian field layout on 32-bit little endian architectures. Fortunately, those ptr32 accessors were never used within the kernel, and only meant as a convenience for user-space. Remove those and replace the whole rseq_cs union by a __u64 type, as this is the only thing really needed to express the ABI. Document how 32-bit architectures are meant to interact with this field. Fixes: ec9c82e03a74 ("rseq: uapi: Declare rseq_cs field as union, update includes") Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Florian Weimer <fw@deneb.enyo.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-api@vger.kernel.org Cc: Peter Zijlstra <peterz@infradead.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Watson <davejwatson@fb.com> Cc: Paul Turner <pjt@google.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Russell King <linux@arm.linux.org.uk> Cc: "H . Peter Anvin" <hpa@zytor.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christian Brauner <christian.brauner@ubuntu.com> Cc: Ben Maurer <bmaurer@fb.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Joel Fernandes <joelaf@google.com> Cc: Paul E. McKenney <paulmck@kernel.org> --- include/uapi/linux/rseq.h | 20 ++++---------------- kernel/rseq.c | 8 ++++---- 2 files changed, 8 insertions(+), 20 deletions(-)