ghsa-frr9-gqr3-75hc
Vulnerability from github
Published
2024-10-21 18:30
Modified
2024-11-08 18:30
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Details

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

ext4: fix double brelse() the buffer of the extents path

In ext4_ext_try_to_merge_up(), set path[1].p_bh to NULL after it has been released, otherwise it may be released twice. An example of what triggers this is as follows:

split2 map split1 |--------|-------|--------|

ext4_ext_map_blocks ext4_ext_handle_unwritten_extents ext4_split_convert_extents // path->p_depth == 0 ext4_split_extent // 1. do split1 ext4_split_extent_at |ext4_ext_insert_extent | ext4_ext_create_new_leaf | ext4_ext_grow_indepth | le16_add_cpu(&neh->eh_depth, 1) | ext4_find_extent | // return -ENOMEM |// get error and try zeroout |path = ext4_find_extent | path->p_depth = 1 |ext4_ext_try_to_merge | ext4_ext_try_to_merge_up | path->p_depth = 0 | brelse(path[1].p_bh) ---> not set to NULL here |// zeroout success // 2. update path ext4_find_extent // 3. do split2 ext4_split_extent_at ext4_ext_insert_extent ext4_ext_create_new_leaf ext4_ext_grow_indepth le16_add_cpu(&neh->eh_depth, 1) ext4_find_extent path[0].p_bh = NULL; path->p_depth = 1 read_extent_tree_block ---> return err // path[1].p_bh is still the old value ext4_free_ext_path ext4_ext_drop_refs // path->p_depth == 1 brelse(path[1].p_bh) ---> brelse a buffer twice

Finally got the following WARRNING when removing the buffer from lru:

============================================ VFS: brelse: Trying to free free buffer WARNING: CPU: 2 PID: 72 at fs/buffer.c:1241 __brelse+0x58/0x90 CPU: 2 PID: 72 Comm: kworker/u19:1 Not tainted 6.9.0-dirty #716 RIP: 0010:__brelse+0x58/0x90 Call Trace: __find_get_block+0x6e7/0x810 bdev_getblk+0x2b/0x480 __ext4_get_inode_loc+0x48a/0x1240 ext4_get_inode_loc+0xb2/0x150 ext4_reserve_inode_write+0xb7/0x230 __ext4_mark_inode_dirty+0x144/0x6a0 ext4_ext_insert_extent+0x9c8/0x3230 ext4_ext_map_blocks+0xf45/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] ============================================

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{
   affected: [],
   aliases: [
      "CVE-2024-49882",
   ],
   database_specific: {
      cwe_ids: [
         "CWE-415",
      ],
      github_reviewed: false,
      github_reviewed_at: null,
      nvd_published_at: "2024-10-21T18:15:10Z",
      severity: "HIGH",
   },
   details: "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix double brelse() the buffer of the extents path\n\nIn ext4_ext_try_to_merge_up(), set path[1].p_bh to NULL after it has been\nreleased, otherwise it may be released twice. An example of what triggers\nthis is as follows:\n\n  split2    map    split1\n|--------|-------|--------|\n\next4_ext_map_blocks\n ext4_ext_handle_unwritten_extents\n  ext4_split_convert_extents\n   // path->p_depth == 0\n   ext4_split_extent\n     // 1. do split1\n     ext4_split_extent_at\n       |ext4_ext_insert_extent\n       |  ext4_ext_create_new_leaf\n       |    ext4_ext_grow_indepth\n       |      le16_add_cpu(&neh->eh_depth, 1)\n       |    ext4_find_extent\n       |      // return -ENOMEM\n       |// get error and try zeroout\n       |path = ext4_find_extent\n       |  path->p_depth = 1\n       |ext4_ext_try_to_merge\n       |  ext4_ext_try_to_merge_up\n       |    path->p_depth = 0\n       |    brelse(path[1].p_bh)  ---> not set to NULL here\n       |// zeroout success\n     // 2. update path\n     ext4_find_extent\n     // 3. do split2\n     ext4_split_extent_at\n       ext4_ext_insert_extent\n         ext4_ext_create_new_leaf\n           ext4_ext_grow_indepth\n             le16_add_cpu(&neh->eh_depth, 1)\n           ext4_find_extent\n             path[0].p_bh = NULL;\n             path->p_depth = 1\n             read_extent_tree_block  ---> return err\n             // path[1].p_bh is still the old value\n             ext4_free_ext_path\n               ext4_ext_drop_refs\n                 // path->p_depth == 1\n                 brelse(path[1].p_bh)  ---> brelse a buffer twice\n\nFinally got the following WARRNING when removing the buffer from lru:\n\n============================================\nVFS: brelse: Trying to free free buffer\nWARNING: CPU: 2 PID: 72 at fs/buffer.c:1241 __brelse+0x58/0x90\nCPU: 2 PID: 72 Comm: kworker/u19:1 Not tainted 6.9.0-dirty #716\nRIP: 0010:__brelse+0x58/0x90\nCall Trace:\n <TASK>\n __find_get_block+0x6e7/0x810\n bdev_getblk+0x2b/0x480\n __ext4_get_inode_loc+0x48a/0x1240\n ext4_get_inode_loc+0xb2/0x150\n ext4_reserve_inode_write+0xb7/0x230\n __ext4_mark_inode_dirty+0x144/0x6a0\n ext4_ext_insert_extent+0x9c8/0x3230\n ext4_ext_map_blocks+0xf45/0x2dc0\n ext4_map_blocks+0x724/0x1700\n ext4_do_writepages+0x12d6/0x2a70\n[...]\n============================================",
   id: "GHSA-frr9-gqr3-75hc",
   modified: "2024-11-08T18:30:44Z",
   published: "2024-10-21T18:30:57Z",
   references: [
      {
         type: "ADVISORY",
         url: "https://nvd.nist.gov/vuln/detail/CVE-2024-49882",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/230ee0535d01478bad9a3037292043f39b9be10b",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/32bbb59e3f18facd7201bef110010bf35819b8c3",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/68a69cf60660c73990c1875f94a5551600b04775",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/7633407ca4ab8be2916ab214eb44ccebc6a50e1a",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/78bbc3d15b6f443acb26e94418c445bac940d414",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/b6c29c8f3d7cb67b505f3b2f6c242d52298d1f2e",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/d4574bda63906bf69660e001470bfe1a0ac524ae",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/dcaa6c31134c0f515600111c38ed7750003e1b9c",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/f9fd47c9d9548f9e47fa60098eab99dde175401d",
      },
   ],
   schema_version: "1.4.0",
   severity: [
      {
         score: "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
         type: "CVSS_V3",
      },
   ],
}


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