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Wong" Subject: [PATCH] ext4: Verify fast symlink length Date: Thu, 6 Feb 2025 10:44:55 +0100 Message-ID: <20250206094454.20522-2-jack@suse.cz> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1465; i=jack@suse.cz; h=from:subject; bh=ldH4oFnFwYY6FL4L5DSyJxwJBXzk8/t/Qj51E5FMMSQ=; b=owEBbQGS/pANAwAIAZydqgc/ZEDZAcsmYgBnpISWLhWpQ1oxnzvAWBDPqRnQgUQGOtREGv7TQbts C+B87H2JATMEAAEIAB0WIQSrWdEr1p4yirVVKBycnaoHP2RA2QUCZ6SElgAKCRCcnaoHP2RA2eiVB/ 9gWbXUOvHuN+zRbgkq83P+i/tZnbGY+PCG6Rxj20sz+3GFd0RgDnyvJPS97PzYaX1KFUFLcv/w339b ciCGG9a2RfyMRKN8xT2BEVws4RarI7VGFmcGS8hgXEaJuSOfz0G95/fk7jIJg22VJz892NuhkjpkCj W0QUjwJgAB9U+03lVSZjUG+GMFniAuDVQMq6fTl4H7f/eVYkqdHJ9yFPyIAqf0Gz9h6d1YREiPReXR lDQwHrTrwBn6oMky6SU7j3ZUv0Bin+ypwSrw+wS2bJRBZRqPmt7UNdc/OkMF+9GSEj2a9CnIDJkL1k nieR8F49fBkofd2EhDfGb5HjzcSXB2 X-Developer-Key: i=jack@suse.cz; a=openpgp; fpr=93C6099A142276A28BBE35D815BC833443038D8C Content-Transfer-Encoding: 8bit X-Spam-Level: X-Spamd-Result: default: False [-1.30 / 50.00]; BAYES_HAM(-3.00)[99.99%]; SUSPICIOUS_RECIPS(1.50)[]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_TLS_LAST(0.00)[]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TAGGED_RCPT(0.00)[48a99e426f29859818c0]; RCVD_COUNT_THREE(0.00)[3]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; RCPT_COUNT_FIVE(0.00)[5]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.cz:email,suse.cz:mid] X-Spam-Score: -1.30 X-Spam-Flag: NO Verify fast symlink length stored in inode->i_size matches the string stored in the inode to avoid surprises from corrupted filesystems. Reported-by: syzbot+48a99e426f29859818c0@syzkaller.appspotmail.com Tested-by: syzbot+48a99e426f29859818c0@syzkaller.appspotmail.com Fixes: bae80473f7b0 ("ext4: use inode_set_cached_link()") Suggested-by: "Darrick J. Wong" Signed-off-by: Jan Kara --- fs/ext4/inode.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 7c54ae5fcbd4..64e280fed911 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -5007,8 +5007,16 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino, inode->i_op = &ext4_encrypted_symlink_inode_operations; } else if (ext4_inode_is_fast_symlink(inode)) { inode->i_op = &ext4_fast_symlink_inode_operations; - nd_terminate_link(ei->i_data, inode->i_size, - sizeof(ei->i_data) - 1); + if (inode->i_size == 0 || + inode->i_size >= sizeof(ei->i_data) || + strnlen((char *)ei->i_data, inode->i_size + 1) != + inode->i_size) { + ext4_error_inode(inode, function, line, 0, + "invalid fast symlink length %llu", + (unsigned long long)inode->i_size); + ret = -EFSCORRUPTED; + goto bad_inode; + } inode_set_cached_link(inode, (char *)ei->i_data, inode->i_size); } else { -- 2.43.0