CVE-2022-49276: Missing Release of Memory after Effective Lifetime

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

jffs2: fix memory leak in jffs2_scan_medium

If an error is returned in jffs2_scan_eraseblock() and some memory has been added to the jffs2_summary *s, we can observe the following kmemleak report:

-------------------------------------------- unreferenced object 0xffff88812b889c40 (size 64): comm "mount", pid 692, jiffies 4294838325 (age 34.288s) hex dump (first 32 bytes): 40 48 b5 14 81 88 ff ff 01 e0 31 00 00 00 50 00 @H........1...P. 00 00 01 00 00 00 01 00 00 00 02 00 00 00 09 08 ................ backtrace: [<ffffffffae93a3a3>] __kmalloc+0x613/0x910 [<ffffffffaf423b9c>] jffs2_sum_add_dirent_mem+0x5c/0xa0 [<ffffffffb0f3afa8>] jffs2_scan_medium.cold+0x36e5/0x4794 [<ffffffffb0f3dbe1>] jffs2_do_mount_fs.cold+0xa7/0x2267 [<ffffffffaf40acf3>] jffs2_do_fill_super+0x383/0xc30 [<ffffffffaf40c00a>] jffs2_fill_super+0x2ea/0x4c0 [<ffffffffb0315d64>] mtd_get_sb+0x254/0x400 [<ffffffffb0315f5f>] mtd_get_sb_by_nr+0x4f/0xd0 [<ffffffffb0316478>] get_tree_mtd+0x498/0x840 [<ffffffffaf40bd15>] jffs2_get_tree+0x25/0x30 [<ffffffffae9f358d>] vfs_get_tree+0x8d/0x2e0 [<ffffffffaea7a98f>] path_mount+0x50f/0x1e50 [<ffffffffaea7c3d7>] do_mount+0x107/0x130 [<ffffffffaea7c5c5>] __se_sys_mount+0x1c5/0x2f0 [<ffffffffaea7c917>] __x64_sys_mount+0xc7/0x160 [<ffffffffb10142f5>] do_syscall_64+0x45/0x70 unreferenced object 0xffff888114b54840 (size 32): comm "mount", pid 692, jiffies 4294838325 (age 34.288s) hex dump (first 32 bytes): c0 75 b5 14 81 88 ff ff 02 e0 02 00 00 00 02 00 .u.............. 00 00 84 00 00 00 44 00 00 00 6b 6b 6b 6b 6b a5 ......D...kkkkk. backtrace: [<ffffffffae93be24>] kmem_cache_alloc_trace+0x584/0x880 [<ffffffffaf423b04>] jffs2_sum_add_inode_mem+0x54/0x90 [<ffffffffb0f3bd44>] jffs2_scan_medium.cold+0x4481/0x4794 [...] unreferenced object 0xffff888114b57280 (size 32): comm "mount", pid 692, jiffies 4294838393 (age 34.357s) hex dump (first 32 bytes): 10 d5 6c 11 81 88 ff ff 08 e0 05 00 00 00 01 00 ..l............. 00 00 38 02 00 00 28 00 00 00 6b 6b 6b 6b 6b a5 ..8...(...kkkkk. backtrace: [<ffffffffae93be24>] kmem_cache_alloc_trace+0x584/0x880 [<ffffffffaf423c34>] jffs2_sum_add_xattr_mem+0x54/0x90 [<ffffffffb0f3a24f>] jffs2_scan_medium.cold+0x298c/0x4794 [...] unreferenced object 0xffff8881116cd510 (size 16): comm "mount", pid 692, jiffies 4294838395 (age 34.355s) hex dump (first 16 bytes): 00 00 00 00 00 00 00 00 09 e0 60 02 00 00 6b a5 ..........`...k. backtrace: [<ffffffffae93be24>] kmem_cache_alloc_trace+0x584/0x880 [<ffffffffaf423cc4>] jffs2_sum_add_xref_mem+0x54/0x90 [<ffffffffb0f3b2e3>] jffs2_scan_medium.cold+0x3a20/0x4794 [...] --------------------------------------------

Therefore, we should call jffs2_sum_reset_collected(s) on exit to release the memory added in s. In addition, a new tag "out_buf" is added to prevent the NULL pointer reference caused by s being NULL. (thanks to Zhang Yi for this analysis)