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authorMatthew Wilcox (Oracle) <willy@infradead.org>2020-11-21 22:17:08 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2020-11-22 10:48:22 -0800
commit4349a83a3190c1d4414371161b0f4a4c3ccd3f9d (patch)
tree2fd2f5f292e1570966e1da974b635a62a5acdcd2
parenta927bd6ba952d13c52b8b385030943032f659a3e (diff)
downloadlinux-stericsson-4349a83a3190c1d4414371161b0f4a4c3ccd3f9d.tar.gz
mm: fix readahead_page_batch for retry entries
Both btrfs and fuse have reported faults caused by seeing a retry entry instead of the page they were looking for. This was caused by a missing check in the iterator. As can be seen in the below panic log, the accessing 0x402 causes a panic. In the xarray.h, 0x402 means RETRY_ENTRY. BUG: kernel NULL pointer dereference, address: 0000000000000402 CPU: 14 PID: 306003 Comm: as Not tainted 5.9.0-1-amd64 #1 Debian 5.9.1-1 Hardware name: Lenovo ThinkSystem SR665/7D2VCTO1WW, BIOS D8E106Q-1.01 05/30/2020 RIP: 0010:fuse_readahead+0x152/0x470 [fuse] Code: 41 8b 57 18 4c 8d 54 10 ff 4c 89 d6 48 8d 7c 24 10 e8 d2 e3 28 f9 48 85 c0 0f 84 fe 00 00 00 44 89 f2 49 89 04 d4 44 8d 72 01 <48> 8b 10 41 8b 4f 1c 48 c1 ea 10 83 e2 01 80 fa 01 19 d2 81 e2 01 RSP: 0018:ffffad99ceaebc50 EFLAGS: 00010246 RAX: 0000000000000402 RBX: 0000000000000001 RCX: 0000000000000002 RDX: 0000000000000000 RSI: ffff94c5af90bd98 RDI: ffffad99ceaebc60 RBP: ffff94ddc1749a00 R08: 0000000000000402 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000100 R12: ffff94de6c429ce0 R13: ffff94de6c4d3700 R14: 0000000000000001 R15: ffffad99ceaebd68 FS: 00007f228c5c7040(0000) GS:ffff94de8ed80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000402 CR3: 0000001dbd9b4000 CR4: 0000000000350ee0 Call Trace: read_pages+0x83/0x270 page_cache_readahead_unbounded+0x197/0x230 generic_file_buffered_read+0x57a/0xa20 new_sync_read+0x112/0x1a0 vfs_read+0xf8/0x180 ksys_read+0x5f/0xe0 do_syscall_64+0x33/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fixes: 042124cc64c3 ("mm: add new readahead_control API") Reported-by: David Sterba <dsterba@suse.com> Reported-by: Wonhyuk Yang <vvghjk1234@gmail.com> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: <stable@vger.kernel.org> Link: https://lkml.kernel.org/r/20201103142852.8543-1-willy@infradead.org Link: https://lkml.kernel.org/r/20201103124349.16722-1-vvghjk1234@gmail.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/pagemap.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index e1e19c1f9ec9..d5570deff400 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -906,6 +906,8 @@ static inline unsigned int __readahead_batch(struct readahead_control *rac,
xas_set(&xas, rac->_index);
rcu_read_lock();
xas_for_each(&xas, page, rac->_index + rac->_nr_pages - 1) {
+ if (xas_retry(&xas, page))
+ continue;
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageTail(page), page);
array[i++] = page;