Description
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix race in read_extent_buffer_pages() There are reports from tree-checker that detects corrupted nodes, without any obvious pattern so possibly an overwrite in memory. After some debugging it turns out there's a race when reading an extent buffer the uptodate status can be missed. To prevent concurrent reads for the same extent buffer, read_extent_buffer_pages() performs these checks: /* (1) */ if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags)) return 0; /* (2) */ if (test_and_set_bit(EXTENT_BUFFER_READING, &eb->bflags)) goto done; At this point, it seems safe to start the actual read operation. Once that completes, end_bbio_meta_read() does /* (3) */ set_extent_buffer_uptodate(eb); /* (4) */ clear_bit(EXTENT_BUFFER_READING, &eb->bflags); Normally, this is enough to ensure only one read happens, and all other callers wait for it to finish before returning. Unfortunately, there is a racey interleaving: Thread A | Thread B | Thread C ---------+----------+--------- (1) | | | (1) | (2) | | (3) | | (4) | | | (2) | | | (1) When this happens, thread B kicks of an unnecessary read. Worse, thread C will see UPTODATE set and return immediately, while the read from thread B is still in progress. This race could result in tree-checker errors like this as the extent buffer is concurrently modified: BTRFS critical (device dm-0): corrupted node, root=256 block=8550954455682405139 owner mismatch, have 11858205567642294356 expect [256, 18446744073709551360] Fix it by testing UPTODATE again after setting the READING bit, and if it's been set, skip the unnecessary read. [ minor update of changelog ]
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
d7172f52e9933b6ec9305e7fe6e829e3939dba04 to < 0427c8ef8bbb7f304de42ef51d69c960e165e052affectedd7172f52e9933b6ec9305e7fe6e829e3939dba04 to < 3a25878a3378adce5d846300c9570f15aa7f7a80affectedd7172f52e9933b6ec9305e7fe6e829e3939dba04 to < 2885d54af2c2e1d910e20d5c8045bae40e02fbc1affectedd7172f52e9933b6ec9305e7fe6e829e3939dba04 to < ef1e68236b9153c27cb7cf29ead0c532870d4215affected
Linux Linux
Default version status: affected
6.5affected0 to < 6.5unaffected6.6.24 to ≤ 6.6.*unaffected6.7.12 to ≤ 6.7.*unaffected6.8.3 to ≤ 6.8.*unaffected6.9 to ≤ *unaffected