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| author | Mikulas Patocka <mpatocka@redhat.com> | 2022-08-09 21:32:13 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-08-17 16:13:41 +0300 |
| commit | 56761b355ded0b32272da84383199c5ede931561 (patch) | |
| tree | 22b221ec7bf79d4ac30a8cc37a08f119dcec58c8 | |
| parent | 24cdb1e7ee12e5292dc05e122075d5f8f74584cf (diff) | |
| download | linux-56761b355ded0b32272da84383199c5ede931561.tar.xz | |
add barriers to buffer_uptodate and set_buffer_uptodate
commit d4252071b97d2027d246f6a82cbee4d52f618b47 upstream.
Let's have a look at this piece of code in __bread_slow:
get_bh(bh);
bh->b_end_io = end_buffer_read_sync;
submit_bh(REQ_OP_READ, 0, bh);
wait_on_buffer(bh);
if (buffer_uptodate(bh))
return bh;
Neither wait_on_buffer nor buffer_uptodate contain any memory barrier.
Consequently, if someone calls sb_bread and then reads the buffer data,
the read of buffer data may be executed before wait_on_buffer(bh) on
architectures with weak memory ordering and it may return invalid data.
Fix this bug by adding a memory barrier to set_buffer_uptodate and an
acquire barrier to buffer_uptodate (in a similar way as
folio_test_uptodate and folio_mark_uptodate).
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | include/linux/buffer_head.h | 25 |
1 files changed, 24 insertions, 1 deletions
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h index c9d1463bb20f..badcc0e3418f 100644 --- a/include/linux/buffer_head.h +++ b/include/linux/buffer_head.h @@ -117,7 +117,6 @@ static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \ * of the form "mark_buffer_foo()". These are higher-level functions which * do something in addition to setting a b_state bit. */ -BUFFER_FNS(Uptodate, uptodate) BUFFER_FNS(Dirty, dirty) TAS_BUFFER_FNS(Dirty, dirty) BUFFER_FNS(Lock, locked) @@ -135,6 +134,30 @@ BUFFER_FNS(Meta, meta) BUFFER_FNS(Prio, prio) BUFFER_FNS(Defer_Completion, defer_completion) +static __always_inline void set_buffer_uptodate(struct buffer_head *bh) +{ + /* + * make it consistent with folio_mark_uptodate + * pairs with smp_load_acquire in buffer_uptodate + */ + smp_mb__before_atomic(); + set_bit(BH_Uptodate, &bh->b_state); +} + +static __always_inline void clear_buffer_uptodate(struct buffer_head *bh) +{ + clear_bit(BH_Uptodate, &bh->b_state); +} + +static __always_inline int buffer_uptodate(const struct buffer_head *bh) +{ + /* + * make it consistent with folio_test_uptodate + * pairs with smp_mb__before_atomic in set_buffer_uptodate + */ + return (smp_load_acquire(&bh->b_state) & (1UL << BH_Uptodate)) != 0; +} + #define bh_offset(bh) ((unsigned long)(bh)->b_data & ~PAGE_MASK) /* If we *know* page->private refers to buffer_heads */ |