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bcachefs: Guard against journal seq overflow

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Wraparound is impractical to handle since in various places we use 0 as
a sentinal value - but 64 bits (or 56, because the btree write buffer
steals a few bits) is enough for all practical purposes.

Reported-by: syzbot+73ed43fbe826227bd4e0@syzkaller.appspotmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2024-11-27 21:58:43 -05:00
parent 9963a14da1
commit b3d82c2f27
2 changed files with 12 additions and 0 deletions
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9
fs/bcachefs/journal.c
View File

@ -382,6 +382,10 @@ static int journal_entry_open(struct journal *j)
if (nr_unwritten_journal_entries(j) == ARRAY_SIZE(j->buf))
return JOURNAL_ERR_max_in_flight;
if (bch2_fs_fatal_err_on(journal_cur_seq(j) >= JOURNAL_SEQ_MAX,
c, "cannot start: journal seq overflow"))
return JOURNAL_ERR_insufficient_devices; /* -EROFS */
BUG_ON(!j->cur_entry_sectors);
buf->expires =
@ -1270,6 +1274,11 @@ int bch2_fs_journal_start(struct journal *j, u64 cur_seq)
bool had_entries = false;
u64 last_seq = cur_seq, nr, seq;
if (cur_seq >= JOURNAL_SEQ_MAX) {
bch_err(c, "cannot start: journal seq overflow");
return -EINVAL;
}
genradix_for_each_reverse(&c->journal_entries, iter, _i) {
i = *_i;

3
fs/bcachefs/journal_types.h
View File

@ -9,6 +9,9 @@
#include "super_types.h"
#include "fifo.h"
/* btree write buffer steals 8 bits for its own purposes: */
#define JOURNAL_SEQ_MAX ((1ULL << 56) - 1)
#define JOURNAL_BUF_BITS 2
#define JOURNAL_BUF_NR (1U << JOURNAL_BUF_BITS)
#define JOURNAL_BUF_MASK (JOURNAL_BUF_NR - 1)