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[209.35.187.178]) by smtp.googlemail.com with ESMTPSA id 956f58d0204a3-67a7a07e163sm2391204d50.8.2026.10.28.15.54.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 28 Oct 2026 15:54:36 -0700 (PDT) Message-ID: Date: Wed, 28 Oct 2026 15:54:34 -0700 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] apparmor: handle diff-encoded states in leftmatch_fb() To: =?UTF-8?Q?Patrick_Gr=C3=B6ssing?= Cc: apparmor@lists.ubuntu.com, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Paul Moore , James Morris , "Serge E . Hallyn" , stable@vger.kernel.org References: <20261026133600.11252-1-invarianztheorem@posteo.com> Content-Language: en-US From: John Johansen Autocrypt: addr=john.johansen@canonical.com; keydata= xsFNBE5mrPoBEADAk19PsgVgBKkImmR2isPQ6o7KJhTTKjJdwVbkWSnNn+o6Up5knKP1f49E BQlceWg1yp/NwbR8ad+eSEO/uma/K+PqWvBptKC9SWD97FG4uB4/caomLEU97sLQMtnvGWdx rxVRGM4anzWYMgzz5TZmIiVTZ43Ou5VpaS1Vz1ZSxP3h/xKNZr/TcW5WQai8u3PWVnbkjhSZ PHv1BghN69qxEPomrJBm1gmtx3ZiVmFXluwTmTgJOkpFol7nbJ0ilnYHrA7SX3CtR1upeUpM a/WIanVO96WdTjHHIa43fbhmQube4txS3FcQLOJVqQsx6lE9B7qAppm9hQ10qPWwdfPy/+0W 6AWtNu5ASiGVCInWzl2HBqYd/Zll93zUq+NIoCn8sDAM9iH+wtaGDcJywIGIn+edKNtK72AM gChTg/j1ZoWH6ZeWPjuUfubVzZto1FMoGJ/SF4MmdQG1iQNtf4sFZbEgXuy9cGi2bomF0zvy BJSANpxlKNBDYKzN6Kz09HUAkjlFMNgomL/cjqgABtAx59L+dVIZfaF281pIcUZzwvh5+JoG eOW5uBSMbE7L38nszooykIJ5XrAchkJxNfz7k+FnQeKEkNzEd2LWc3QF4BQZYRT6PHHga3Rg ykW5+1wTMqJILdmtaPbXrF3FvnV0LRPcv4xKx7B3fGm7ygdoowARAQABzStKb2huIEpvaGFu c2VuIDxqb2huLmpvaGFuc2VuQGNhbm9uaWNhbC5jb20+wsF3BBMBCgAhBQJOjRdaAhsDBQsJ CAcDBRUKCQgLBRYCAwEAAh4BAheAAAoJEAUvNnAY1cPYi0wP/2PJtzzt0zi4AeTrI0w3Rj8E Waa1NZWw4GGo6ehviLfwGsM7YLWFAI8JB7gsuzX/im16i9C3wHYXKs9WPCDuNlMc0rvivqUI JXHHfK7UHtT0+jhVORyyVVvX+qZa7HxdZw3jK+ROqUv4bGnImf31ll99clzo6HpOY59soa8y 66/lqtIgDckcUt/1ou9m0DWKwlSvulL1qmD25NQZSnvB9XRZPpPd4bea1RTa6nklXjznQvTm MdLq5aJ79j7J8k5uLKvE3/pmpbkaieEsGr+azNxXm8FPcENV7dG8Xpd0z06E+fX5jzXHnj69 DXXc3yIvAXsYZrXhnIhUA1kPQjQeNG9raT9GohFPMrK48fmmSVwodU8QUyY7MxP4U6jE2O9L 7v7AbYowNgSYc+vU8kFlJl4fMrX219qU8ymkXGL6zJgtqA3SYHskdDBjtytS44OHJyrrRhXP W1oTKC7di/bb8jUQIYe8ocbrBz3SjjcL96UcQJecSHu0qmUNykgL44KYzEoeFHjr5dxm+DDg OBvtxrzd5BHcIbz0u9ClbYssoQQEOPuFmGQtuSQ9FmbfDwljjhrDxW2DFZ2dIQwIvEsg42Hq 5nv/8NhW1whowliR5tpm0Z0KnQiBRlvbj9V29kJhs7rYeT/dWjWdfAdQSzfoP+/VtPRFkWLr 0uCwJw5zHiBgzsFNBE5mrPoBEACirDqSQGFbIzV++BqYBWN5nqcoR+dFZuQL3gvUSwku6ndZ vZfQAE04dKRtIPikC4La0oX8QYG3kI/tB1UpEZxDMB3pvZzUh3L1EvDrDiCL6ef93U+bWSRi GRKLnNZoiDSblFBST4SXzOR/m1wT/U3Rnk4rYmGPAW7ltfRrSXhwUZZVARyJUwMpG3EyMS2T dLEVqWbpl1DamnbzbZyWerjNn2Za7V3bBrGLP5vkhrjB4NhrufjVRFwERRskCCeJwmQm0JPD IjEhbYqdXI6uO+RDMgG9o/QV0/a+9mg8x2UIjM6UiQ8uDETQha55Nd4EmE2zTWlvxsuqZMgy W7gu8EQsD+96JqOPmzzLnjYf9oex8F/gxBSEfE78FlXuHTopJR8hpjs6ACAq4Y0HdSJohRLn 5r2CcQ5AsPEpHL9rtDW/1L42/H7uPyIfeORAmHFPpkGFkZHHSCQfdP4XSc0Obk1olSxqzCAm uoVmRQZ3YyubWqcrBeIC3xIhwQ12rfdHQoopELzReDCPwmffS9ctIb407UYfRQxwDEzDL+m+ TotTkkaNlHvcnlQtWEfgwtsOCAPeY9qIbz5+i1OslQ+qqGD2HJQQ+lgbuyq3vhefv34IRlyM sfPKXq8AUTZbSTGUu1C1RlQc7fpp8W/yoak7dmo++MFS5q1cXq29RALB/cfpcwARAQABwsFf BBgBCgAJBQJOZqz6AhsMAAoJEAUvNnAY1cPYP9cP/R10z/hqLVv5OXWPOcpqNfeQb4x4Rh4j h/jS9yjes4uudEYU5xvLJ9UXr0wp6mJ7g7CgjWNxNTQAN5ydtacM0emvRJzPEEyujduesuGy a+O6dNgi+ywFm0HhpUmO4sgs9SWeEWprt9tWrRlCNuJX+u3aMEQ12b2lslnoaOelghwBs8IJ r998vj9JBFJgdeiEaKJLjLmMFOYrmW197As7DTZ+R7Ef4gkWusYFcNKDqfZKDGef740Xfh9d yb2mJrDeYqwgKb7SF02Hhp8ZnohZXw8ba16ihUOnh1iKH77Ff9dLzMEJzU73DifOU/aArOWp JZuGJamJ9EkEVrha0B4lN1dh3fuP8EjhFZaGfLDtoA80aPffK0Yc1R/pGjb+O2Pi0XXL9AVe qMkb/AaOl21F9u1SOosciy98800mr/3nynvid0AKJ2VZIfOP46nboqlsWebA07SmyJSyeG8c XA87+8BuXdGxHn7RGj6G+zZwSZC6/2v9sOUJ+nOna3dwr6uHFSqKw7HwNl/PUGeRqgJEVu++ +T7sv9+iY+e0Y+SolyJgTxMYeRnDWE6S77g6gzYYHmcQOWP7ZMX+MtD4SKlf0+Q8li/F9GUL p0rw8op9f0p1+YAhyAd+dXWNKf7zIfZ2ME+0qKpbQnr1oizLHuJX/Telo8KMmHter28DPJ03 lT9Q Organization: Canonical In-Reply-To: <20261026133600.11252-1-invarianztheorem@posteo.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 10/26/26 06:36, Patrick Grössing wrote: > leftmatch_fb(), used by aa_dfa_leftmatch() and therefore by find_attach() > to match profile attachments, open-codes the DFA transition and treats the > default transition as final: > > if (check[pos] == state) > state = next[pos]; > else > state = def[state]; > > For a state flagged MATCH_FLAG_DIFF_ENCODE the default state must instead > be tried again with the same input character, which is what match_char() > does for every other matcher. apparmor_parser emits differentially encoded > DFAs by default when the kernel advertises policy/diff_encode, so larger > attachment patterns end in a non-accepting state and the exec silently > stays unconfined. No conflict is detected, so nothing is audited. > > One visible victim is Ubuntu's firefox profile, whose attachment > > /{usr/lib/firefox{,-esr,-beta,-devedition,-nightly},opt/firefox}/firefox{,-esr,-bin} > > never matches. Firefox then runs unconfined, is moved to unprivileged_userns > and is denied CAP_SYS_ADMIN, losing its user namespace sandbox. The same > profile compiled with -O no-diff-encode attaches. > > Use match_char() in both branches of leftmatch_fb(). > > Fixes: 21f606610502 ("apparmor: improve overlapping domain attachment resolution") > Cc: stable@vger.kernel.org > Link: https://gitlab.com/apparmor/apparmor-kernel/-/issues/8 > Link: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2172229 > Signed-off-by: Patrick Grössing thank you for the patch, unfortunately this issue has already been addressed by daa9ef365c0ed apparmor: convert duplicated dfa transitions to match_char() > --- > Tested on a kernel built from Ubuntu linux 7.0.0-38.38 (upstream 7.0.14): > with this patch the diff-encoded reproducer profile from the GitLab issue > attaches, and the stock Ubuntu firefox profile attaches to > /usr/lib/firefox/firefox-bin (all processes "firefox (unconfined)", no > unprivileged_userns denials). Without it both stay unconfined, also on the > stock 7.0.0-38-generic kernel. Compile-tested with W=1. > Based on apparmor-next as of 2026-10-26. > > security/apparmor/match.c | 16 +++++----------- > 1 file changed, 5 insertions(+), 11 deletions(-) > > diff --git a/security/apparmor/match.c b/security/apparmor/match.c > index 7713484..796126d 100644 > --- a/security/apparmor/match.c > +++ b/security/apparmor/match.c > @@ -751,7 +751,7 @@ static aa_state_t leftmatch_fb(const struct aa_dfa *dfa, aa_state_t start, > u32 *base = BASE_TABLE(dfa); > u32 *next = NEXT_TABLE(dfa); > u32 *check = CHECK_TABLE(dfa); > - aa_state_t state = start, pos; > + aa_state_t state = start; > > AA_BUG(!dfa); > AA_BUG(!str); > @@ -769,13 +769,10 @@ static aa_state_t leftmatch_fb(const struct aa_dfa *dfa, aa_state_t start, > /* default is direct to next state */ > while (*str) { > unsigned int adjust; > + u8 c = equiv[(u8) *str++]; > > wb->history[wb->pos] = state; > - pos = base_idx(base[state]) + equiv[(u8) *str++]; > - if (check[pos] == state) > - state = next[pos]; > - else > - state = def[state]; > + match_char(state, def, base, next, check, c); > if (is_loop(wb, state, &adjust)) { > state = aa_dfa_match(dfa, state, str); > *count -= adjust; > @@ -788,13 +785,10 @@ static aa_state_t leftmatch_fb(const struct aa_dfa *dfa, aa_state_t start, > /* default is direct to next state */ > while (*str) { > unsigned int adjust; > + u8 c = (u8) *str++; > > wb->history[wb->pos] = state; > - pos = base_idx(base[state]) + (u8) *str++; > - if (check[pos] == state) > - state = next[pos]; > - else > - state = def[state]; > + match_char(state, def, base, next, check, c); > if (is_loop(wb, state, &adjust)) { > state = aa_dfa_match(dfa, state, str); > *count -= adjust;