erofs: fix out-of-bound access when z_erofs_gbuf_growsize() partially fails

If z_erofs_gbuf_growsize() partially fails on a global buffer due to
memory allocation failure or fault injection (as reported by syzbot [1]),
new pages need to be freed by comparing to the existing pages to avoid
memory leaks.

However, the old gbuf->pages[] array may not be large enough, which can
lead to null-ptr-deref or out-of-bound access.

Fix this by checking against gbuf->nrpages in advance.

[1] https://lore.kernel.org/r/[email protected]

Reported-by: [email protected]
Fixes: d6db47e571dc ("erofs: do not use pagepool in z_erofs_gbuf_growsize()")
Cc: <[email protected]> # 6.10+
Reviewed-by: Chunhai Guo <[email protected]>
Reviewed-by: Sandeep Dhavale <[email protected]>
Signed-off-by: Gao Xiang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

0 files changed, 0 insertions, 0 deletions