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authorDaniel Borkmann <daniel@iogearbox.net>2017-03-11 18:55:49 +0300
committerDavid S. Miller <davem@davemloft.net>2017-03-13 09:51:34 +0300
commit65869a47f3488253f5fd88cc4f14e0a4e2601a55 (patch)
treee34da15943fbe50adc5aeaac96fce51b0cedf8bf /include
parent1da8ac7c49fb2879ba95006d8bd1095e6870ea1a (diff)
downloadlinux-65869a47f3488253f5fd88cc4f14e0a4e2601a55.tar.xz
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: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
-rw-r--r--include/linux/filter.h16
1 files changed, 12 insertions, 4 deletions
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 0c167fdee5f7..fbf7b39e8103 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -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)