CVE-2026-89786

Summary

In the Linux kernel, the following vulnerability has been resolved:

ext4: fix out-of-bounds read in ext4_read_inline_dir()

ext4_read_inline_dir() can read a dirent header past the end of its inline buffer, triggering a slab-out-of-bounds read during getdents64():

BUG: KASAN: slab-out-of-bounds in __ext4_check_dir_entry Read of size 2 at addr ffff88800f3dd23c by task exploit/148 … __ext4_check_dir_entry ext4_read_inline_dir iterate_dir

The dirent payload lives in a buffer of exactly inline_size bytes:

dir_buf = kmalloc(inline_size, GFP_NOFS);

but iteration runs in a position space extra_offset bytes larger (extra_size = extra_offset + inline_size) so the synthetic "." and ".." land at their block-dir offsets. A dirent is formed at "dir_buf + pos - extra_offset", yet the ext4_check_dir_entry() length argument uses the larger extra_size. A position whose dirent header would extend past extra_size is therefore accepted, and the rescan loop's rec_len probe and ext4_check_dir_entry() dereference de->rec_len before the entry is rejected.

Reject a position whose minimum-size dirent header would not fit within extra_size before forming de, in both the rescan and main loops, and pass inline_size rather than extra_size to ext4_check_dir_entry() so the length check matches the physical buffer.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/d1e7c186555ad65554fd2f2b02f5a539aa35ae48
• https://git.kernel.org/stable/c/5fd20d4e50dd6e460b3ea8e4396f8553d4526f8f
• https://git.kernel.org/stable/c/1a1dea633b724a1c042dbcdb1fed27f410916688
• https://git.kernel.org/stable/c/b060861f662d4826dc700a1c3584243bb3474cfe
• https://git.kernel.org/stable/c/6702c7da86d8cdb88d0fc57166286e115ffeb8c0
• https://git.kernel.org/stable/c/36bf17bb90cdf7a623499b624b05acde4d2feef5
• https://git.kernel.org/stable/c/9333cc809f0a89e001b814155a6cb8903a6274df

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