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Commit 65869a47 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller
Browse files

bpf: improve read-only handling 



Improve bpf_{prog,jit_binary}_{un,}lock_ro() by throwing a
one-time warning in case of an error when the image couldn't
be set read-only, and also mark struct bpf_prog as locked when
bpf_prog_lock_ro() was called.

Reason for the latter is that bpf_prog_unlock_ro() is called from
various places including error paths, and we shouldn't mess with
page attributes when really not needed.

For bpf_jit_binary_unlock_ro() this is not needed as jited flag
implicitly indicates this, thus for archs with ARCH_HAS_SET_MEMORY
we're guaranteed to have a previously locked image. Overall, this
should also help us to identify any further potential issues with
set_memory_*() helpers.

Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1da8ac7c

include/linux/filter.h

+12 −4
Original line number Diff line number Diff line
@@ -409,6 +409,7 @@ struct bpf_prog { 
	u16			pages;		/* Number of allocated pages */

	kmemcheck_bitfield_begin(meta);

	u16			jited:1,	/* Is our filter JIT'ed? */

				locked:1,	/* Program image locked? */

				gpl_compatible:1, /* Is filter GPL compatible? */

				cb_access:1,	/* Is control block accessed? */

				dst_needed:1,	/* Do we need dst entry? */
@@ -554,22 +555,29 @@ static inline bool bpf_prog_was_classic(const struct bpf_prog *prog) 
#ifdef CONFIG_ARCH_HAS_SET_MEMORY

static inline void bpf_prog_lock_ro(struct bpf_prog *fp)

{

	set_memory_ro((unsigned long)fp, fp->pages);

	fp->locked = 1;

	WARN_ON_ONCE(set_memory_ro((unsigned long)fp, fp->pages));

}



static inline void bpf_prog_unlock_ro(struct bpf_prog *fp)

{

	set_memory_rw((unsigned long)fp, fp->pages);

	if (fp->locked) {

		WARN_ON_ONCE(set_memory_rw((unsigned long)fp, fp->pages));

		/* In case set_memory_rw() fails, we want to be the first

		 * to crash here instead of some random place later on.

		 */

		fp->locked = 0;

	}

}



static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr)

{

	set_memory_ro((unsigned long)hdr, hdr->pages);

	WARN_ON_ONCE(set_memory_ro((unsigned long)hdr, hdr->pages));

}



static inline void bpf_jit_binary_unlock_ro(struct bpf_binary_header *hdr)

{

	set_memory_rw((unsigned long)hdr, hdr->pages);

	WARN_ON_ONCE(set_memory_rw((unsigned long)hdr, hdr->pages));

}

#else

static inline void bpf_prog_lock_ro(struct bpf_prog *fp)