| Message ID | 20200324030855.29245-1-wqu@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs-progs: check/lowmem: Fix access on uninitialized memory | expand |
On Tue, Mar 24, 2020 at 11:08:55AM +0800, Qu Wenruo wrote: > [BUG] > There are some reports on fsck/001 test segfault failure with lowmem mode. > > While I failed to reproduce it, valgrind still catches it with the > following output: > > Delete backref in extent [12845056 1048576] > ERROR: file extent [257, 0] has unaligned disk bytenr: 755944791, should be aligned to 4096 > ERROR: file extent[257 0] root 5 owner 5 backref lost > Deleted root 5 item[257, 108, 0] > ==29080== Conditional jump or move depends on uninitialised value(s) > ==29080== at 0x1A81D7: btrfs_release_path (ctree.c:97) > ==29080== by 0x192C33: repair_extent_data_item (mode-lowmem.c:3330) > ==29080== by 0x1962FF: check_leaf_items (mode-lowmem.c:4696) > ==29080== by 0x196ABF: walk_down_tree (mode-lowmem.c:4858) > ==29080== by 0x197762: check_btrfs_root (mode-lowmem.c:5157) > ==29080== by 0x198335: check_chunks_and_extents_lowmem (mode-lowmem.c:5450) > ==29080== by 0x166414: do_check_chunks_and_extents (main.c:8829) > ==29080== by 0x169CF7: cmd_check (main.c:10313) > ==29080== by 0x11CDC6: cmd_execute (commands.h:125) > ==29080== by 0x11D712: main (btrfs.c:386) > ==29080== > > [CAUSE] > In repair_extent_data_item() if we find unaligned file extent, we just > delete it and kick in hole punch procedure. > > The problem is, file extent deletion is done before initializing @path. > And when the deletion is done without problem, we will goto out tag, > which will release @path, containing uninitialized values, and > triggering segfault. > > [FIX] > Don't try to abort trans nor free path if we're going through file > extent deletion routine. > > Fixes: 0617bde3bc15 ("btrfs-progs: lowmem: delete unaligned bytes extent data under repair") > Signed-off-by: Qu Wenruo <wqu@suse.com> Added to devel, thanks.
diff --git a/check/mode-lowmem.c b/check/mode-lowmem.c index 7f734f974d02..1b3f24a397ea 100644 --- a/check/mode-lowmem.c +++ b/check/mode-lowmem.c @@ -3253,7 +3253,7 @@ static int repair_extent_data_item(struct btrfs_root *root, ret = delete_item(root, pathp); if (!ret) err = 0; - goto out; + goto out_no_release; } /* now repair only adds backref */ @@ -3328,6 +3328,7 @@ out: if (trans) btrfs_commit_transaction(trans, root); btrfs_release_path(&path); +out_no_release: if (ret) error("can't repair root %llu extent data item[%llu %llu]", root->objectid, disk_bytenr, num_bytes);
[BUG] There are some reports on fsck/001 test segfault failure with lowmem mode. While I failed to reproduce it, valgrind still catches it with the following output: Delete backref in extent [12845056 1048576] ERROR: file extent [257, 0] has unaligned disk bytenr: 755944791, should be aligned to 4096 ERROR: file extent[257 0] root 5 owner 5 backref lost Deleted root 5 item[257, 108, 0] ==29080== Conditional jump or move depends on uninitialised value(s) ==29080== at 0x1A81D7: btrfs_release_path (ctree.c:97) ==29080== by 0x192C33: repair_extent_data_item (mode-lowmem.c:3330) ==29080== by 0x1962FF: check_leaf_items (mode-lowmem.c:4696) ==29080== by 0x196ABF: walk_down_tree (mode-lowmem.c:4858) ==29080== by 0x197762: check_btrfs_root (mode-lowmem.c:5157) ==29080== by 0x198335: check_chunks_and_extents_lowmem (mode-lowmem.c:5450) ==29080== by 0x166414: do_check_chunks_and_extents (main.c:8829) ==29080== by 0x169CF7: cmd_check (main.c:10313) ==29080== by 0x11CDC6: cmd_execute (commands.h:125) ==29080== by 0x11D712: main (btrfs.c:386) ==29080== [CAUSE] In repair_extent_data_item() if we find unaligned file extent, we just delete it and kick in hole punch procedure. The problem is, file extent deletion is done before initializing @path. And when the deletion is done without problem, we will goto out tag, which will release @path, containing uninitialized values, and triggering segfault. [FIX] Don't try to abort trans nor free path if we're going through file extent deletion routine. Fixes: 0617bde3bc15 ("btrfs-progs: lowmem: delete unaligned bytes extent data under repair") Signed-off-by: Qu Wenruo <wqu@suse.com> --- check/mode-lowmem.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)